# Approximately two-dimensional harmonic $$(p_{1},h_{1})$$-$$(p_{2},h_{2})$$-convex functions and related integral inequalities

## Abstract

The aim of this study is to introduce the notion of two-dimensional approximately harmonic $$(p_{1},h_{1})$$-$$(p_{2},h_{2})$$-convex functions. We show that the new class covers many new and known extensions of harmonic convex functions. We formulate several new refinements of Hermite–Hadamard like inequalities involving two-dimensional approximately harmonic $$(p_{1},h_{1})$$-$$(p_{2},h_{2})$$-convex functions. We discuss in detail the special cases that can be deduced from the main results of the paper.

## 1 Introduction and preliminaries

A function $$f:I\subset \mathbb{R}\to \mathbb{R}$$ is said to be convex, if

$$f\bigl((1-t)x+ty\bigr)\leq (1-t)f(x)+tf(y),\quad \forall x,y\in I,t\in [0,1].$$

In recent years the classical concepts of convex functions have been extended and generalized in different directions using innovative and novel ideas. Işcan [1] introduced the class of harmonic convex functions.

A function $$f:I\subset (0,\infty )\to \mathbb{R}$$ is said to be harmonically convex if

\begin{aligned} f \biggl(\frac{xy}{(1-t)x+ty} \biggr)\leq tf(x)+(1-t)f(y),\quad \forall x,y\in I,t\in [0,1]. \end{aligned}

Noor et al. [2] generalized the notion of harmonic convex functions and gave the definition of harmonically h-convex functions. This class contains several other classes of harmonic convex functions as well. In [3], the authors introduced the definition of p-harmonic convex function.

A function $$f:I\subset (0,\infty )\to \mathbb{R}$$ is said to be p-harmonically convex if

\begin{aligned} f \biggl(\frac{x^{p}y^{p}}{(1-t)x^{p}+ty^{p}} \biggr)^{\frac{1}{p}} \leq tf(x)+(1-t)f(y),\quad \forall x,y\in I,t\in [0,1] \end{aligned}

holds, where I is a p-harmonic convex set.

Noor et al. [4] also extended the class of harmonic convex functions on coordinates and introduced the class of coordinated harmonic convex functions.

Consider the rectangle $$\Omega = [a,b]\times [c,d]\subset (0,\infty )\times (0,\infty )$$. A function $$f: \Omega \rightarrow \mathbb{R}$$ is said to be two-dimensional harmonically convex function on Ω if

\begin{aligned} &f \biggl(\frac{xy}{tx+(1-t)y},\frac{uw}{ru+(1-r)w} \biggr) \\ &\quad\leq \operatorname{tr} f(y,w)+t(1-r) f(y,u)+(1-t)r f(x,w)+(1-t) (1-r) f(x,u), \end{aligned}

whenever $$x,y \in [a,b], u,w \in [c,d]$$, and $$t,r \in [0,1]$$. Recently, Awan et al. [5] gave the definition of approximately harmonic h-convex functions depending on a metric function $$d:X\times X \to \mathbb{R}$$ where $$(X,\Vert \cdot\Vert )$$ is a real normed space. Let $$h:(0,1)\to \mathbb{R}$$ and Θ be a harmonic convex subset of X. A function $$f:\Theta \to \mathbb{R}$$ is an approximately harmonic h-convex function if

\begin{aligned} f \biggl(\frac{xy}{(1-t)x+ty} \biggr)\leq h(t)f(x)+h(1-t)f(y)+d(x,y), \quad\forall x,y \in \Theta,t\in [0,1]. \end{aligned}

For more and recent details on convexity and its generalizations, see [618].

Theory of convexity also played a significant role in the development of theory of inequalities. Many famously known results in inequalities theory can be obtained using the convexity property of the functions. Hermite–Hadamard double inequality is one of the most intensively studied results involving convex functions. This result provides us a necessary and sufficient condition for a function to be convex. For interesting details on Hermite–Hadamard inequality and its generalizations, see [15, 19].

## 2 New notions

In this section, we define the class of two-dimensional approximately harmonic $$(p_{1},h_{1})$$-$$(p_{2},h_{2})$$-convex functions. We also discuss that for suitable choices we get several other new classes of harmonic convexity.

### Definition 1

Consider the rectangle $$\Omega = [a,b]\times [c,d]\subset (0,\infty )\times (0,\infty )$$. A function $$f: \Omega \rightarrow \mathbb{R}$$ is said to be a two-dimensional approximately harmonic $$(p_{1},h_{1})$$-$$(p_{2},h_{2})$$-convex function if

\begin{aligned} &f \biggl( \biggl[\frac{x^{p_{1}}y^{p_{1}}}{tx^{p_{1}}+(1-t)y^{p_{1}}} \biggr]^{\frac{1}{p_{1}}}, \biggl[ \frac{u^{p_{2}}w^{p_{2}}}{ru^{p_{2}}+(1-r)w^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}} \biggr) \\ &\quad\leq h_{1}(t)h_{2}(r) f(y,w)+h_{1}(t)h_{2}(1-r) f(y,u) \\ &\qquad{} +h_{1}(1-t)h_{2}(r )f(x,w)+h_{1}(1-t)h_{2}(1-r) f(x,u)+\Delta (x,y)+ \Delta (u,w), \end{aligned}

whenever $$x,y \in [a,b], u,w \in [c,d]$$, and $$t,r \in [0,1]$$.

We now discuss some special cases of Definition 1.

I. If we take $$\Delta (x,y)=\epsilon (\| x^{p_{1}}-y^{p_{1}} \|)^{\gamma }$$ and $$\Delta (u,w)=\epsilon (\| u^{p_{2}}-w^{p_{2}} \|)^{\gamma }$$ for some $$\epsilon \in \mathbb{R}$$ and $$\gamma >1$$ in Definition 1, we have a new definition of γ-paraharmonic $$(p_{1},h_{1})$$-$$(p_{2},h_{2})$$-convex function of higher order.

### Definition 2

Consider the rectangle $$\Omega = [a,b]\times [c,d]\subset (0,\infty )\times (0,\infty )$$. A function $$f: \Omega \rightarrow \mathbb{R}$$ is said to be a two-dimensional γ-paraharmonic $$(p_{1},h_{1})$$-$$(p_{2},h_{2})$$-convex function of higher order if

\begin{aligned} &f \biggl( \biggl[\frac{x^{p_{1}}y^{p_{1}}}{tx^{p_{1}}+(1-t)y^{p_{1}}} \biggr]^{\frac{1}{p_{1}}}, \biggl[ \frac{u^{p_{2}}w^{p_{2}}}{ru^{p_{2}}+(1-r)w^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}} \biggr) \\ &\quad\leq h_{1}(t)h_{2}(r) f(y,w)+h_{1}(t)h_{2}(1-r) f(y,u) \\ &\qquad{} +h_{1}(1-t)h_{2}(r )f(x,w)+h_{1}(1-t)h_{2}(1-r) f(x,u)+ \epsilon \bigl( \bigl\Vert x^{p_{1}}-y^{p_{1}} \bigr\Vert \bigr)^{\gamma }\\ &\qquad{}+\epsilon \bigl( \bigl\Vert u^{p_{2}}-w^{p_{2}} \bigr\Vert \bigr)^{\gamma }, \end{aligned}

whenever $$x,y \in [a,b], u,w \in [c,d]$$, and $$t,r \in [0,1]$$.

II. If we take $$\Delta (x,y)=\epsilon (\| x^{p_{1}}-y^{p_{1}} \|)$$ and $$\Delta (u,w)=\epsilon (\|u^{p_{2}}-w^{p_{2}}\|)$$ for some $$\epsilon \in \mathbb{R}$$ and in Definition 1, we have a new definition of ϵ-paraharmonic $$(p_{1},h_{1})$$-$$(p_{2},h_{2})$$-convex function.

### Definition 3

Consider the rectangle $$\Omega =[a,b]\times [c,d]\subset (0,\infty )\times (0,\infty )$$. A function $$f:\Omega \rightarrow \mathbb{R}$$ is said to be a two-dimensional ϵ-paraharmonic $$(p_{1},h_{1})$$-$$(p_{2},h_{2})$$-convex function if

\begin{aligned} &f \biggl( \biggl[\frac{x^{p_{1}}y^{p_{1}}}{tx^{p_{1}}+(1-t)y^{p_{1}}} \biggr]^{\frac{1}{p_{1}}}, \biggl[ \frac{u^{p_{2}}w^{p_{2}}}{ru^{p_{2}}+(1-r)w^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}} \biggr) \\ &\quad\leq h_{1}(t)h_{2}(r) f(y,w)+h_{1}(t)h_{2}(1-r) f(y,u) \\ &\qquad{} +h_{1}(1-t)h_{2}(r )f(x,w)+h_{1}(1-t)h_{2}(1-r) f(x,u) \\ &\qquad{} +\epsilon \bigl( \bigl\Vert x^{p_{1}}-y^{p_{1}} \bigr\Vert \bigr)+\epsilon \bigl( \bigl\Vert u^{p_{2}}-w^{p_{2}} \bigr\Vert \bigr), \end{aligned}

whenever $$x,y \in [a,b], u,w \in [c,d]$$, and $$t,r \in [0,1]$$.

III. If we take $$\Delta (x,y)=-\mu (t^{\sigma }(1-t)+t(1-t)^{\sigma } ) ( \Vert \frac{1}{y^{p_{1}}}-\frac{1}{x^{p_{1}}} \Vert )^{\sigma }$$ and

$$\Delta (u,w)=-\mu (r^{\sigma }(1-r)+r(1-r)^{\sigma } ) ( \Vert \frac{1}{w^{p_{2}}}-\frac{1}{u^{p_{2}}} \Vert )^{\sigma }$$ for some $$\mu >0$$ and $$\sigma >0$$ in Definition 1, we have a new definition of two-dimensional harmonically strong $$(p_{1},h_{1})$$-$$(p_{2},h_{2})$$-convex function of higher order.

### Definition 4

Consider the rectangle $$\Omega = [a,b]\times [c,d]\subset (0,\infty )\times (0,\infty )$$. A function $$f: \Omega \rightarrow \mathbb{R}$$ is said to be a two-dimensional harmonically strong $$(p_{1},h_{1})$$-$$(p_{2},h_{2})$$-convex function of higher order if

\begin{aligned} &f \biggl( \biggl[\frac{x^{p_{1}}y^{p_{1}}}{tx^{p_{1}}+(1-t)y^{p_{1}}} \biggr]^{\frac{1}{p_{1}}}, \biggl[ \frac{u^{p_{2}}w^{p_{2}}}{ru^{p_{2}}+(1-r)w^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}} \biggr) \\ &\quad\leq h_{1}(t)h_{2}(r) f(y,w)+h_{1}(t)h_{2}(1-r) f(y,u) \\ &\qquad{} +h_{1}(1-t)h_{2}(r )f(x,w)+h_{1}(1-t)h_{2}(1-r) f(x,u) \\ &\qquad{} -\mu \bigl(t^{\sigma }(1-t)+t(1-t)^{\sigma } \bigr) \biggl( \biggl\Vert \frac{1}{y^{p_{1}}}-\frac{1}{x^{p_{1}}} \biggr\Vert \biggr)^{ \sigma }\\ &\qquad{}- \mu \bigl(r^{\sigma }(1-r)+r(1-r)^{\sigma } \bigr) \biggl( \biggl\Vert \frac{1}{w^{p_{2}}}-\frac{1}{u^{p_{2}}} \biggr\Vert \biggr)^{ \sigma }, \end{aligned}

whenever $$x,y \in [a,b], u,w \in [c,d], \sigma >0$$, and $$t,r \in [0,1]$$.

IV. If we take $$\sigma =2$$ in Definition 4, then $$\Delta (x,y)=-\mu t(1-t) ( \Vert \frac{1}{y^{p_{1}}}- \frac{1}{x^{p_{1}}} \Vert )^{2}$$ and $$\Delta (u,w)=-\mu r(1-r) ( \Vert \frac{1}{w^{p_{2}}}- \frac{1}{u^{p_{2}}} \Vert )^{2}$$ for some $$\mu >0$$ in Definition 1, then

### Definition 5

Consider the rectangle $$\Omega = [a,b]\times [c,d]\subset (0,\infty )\times (0,\infty )$$. A function $$f: \Omega \rightarrow \mathbb{R}$$ is said to be a two-dimensional harmonically strong $$(p_{1},h_{1})$$-$$(p_{2},h_{2})$$-convex function if

\begin{aligned} &f \biggl( \biggl[\frac{x^{p_{1}}y^{p_{1}}}{tx^{p_{1}}+(1-t)y^{p_{1}}} \biggr]^{\frac{1}{p_{1}}}, \biggl[ \frac{u^{p_{2}}w^{p_{2}}}{ru^{p_{2}}+(1-r)w^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}} \biggr) \\ &\quad\leq h_{1}(t)h_{2}(r) f(y,w)+h_{1}(t)h_{2}(1-r) f(y,u)\\ &\qquad{}+h_{1}(1-t)h_{2}(r )f(x,w)+h_{1}(1-t)h_{2}(1-r) f(x,u) \\ &\qquad{} -\mu t(1-t) \biggl( \biggl\Vert \frac{1}{y^{p_{1}}}- \frac{1}{x^{p_{1}}} \biggr\Vert \biggr)^{2}-\mu r(1-r) \biggl( \biggl\Vert \frac{1}{w^{p_{2}}}- \frac{1}{u^{p_{2}}} \biggr\Vert \biggr)^{2}, \end{aligned}

whenever $$x,y \in [a,b], u,w \in [c,d]$$, and $$t,r \in [0,1]$$.

V. If we take $$\Delta (x,y)=\mu t(1-t) (\frac{1}{y^{p_{1}}}- \frac{1}{x^{p_{1}}} )^{2}$$ and $$\Delta (u,w)=\mu r(1-r) (\frac{1}{w^{p_{2}}}- \frac{1}{u^{p_{2}}} )^{2}$$ for some $$\mu >0$$ in Definition 1, then

### Definition 6

Consider the rectangle $$\Omega = [a,b]\times [c,d]\subset (0,\infty )\times (0,\infty )$$. A function $$f: \Omega \rightarrow \mathbb{R}$$ is said to be a two-dimensional harmonically relaxed $$(p_{1},h_{1})$$-$$(p_{2},h_{2})$$-convex function if

\begin{aligned} &f \biggl( \biggl[\frac{x^{p_{1}}y^{p_{1}}}{tx^{p_{1}}+(1-t)y^{p_{1}}} \biggr]^{\frac{1}{p_{1}}}, \biggl[ \frac{u^{p_{2}}w^{p_{2}}}{ru^{p_{2}}+(1-r)w^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}} \biggr) \\ &\quad\leq h_{1}(t)h_{2}(r) f(y,w)+h_{1}(t)h_{2}(1-r) f(y,u)+h_{1}(1-t)h_{2}(r )f(x,w)\\ &\qquad{}+h_{1}(1-t)h_{2}(1-r) f(x,u) \\ & \qquad{}+\mu t(1-t) \biggl(\frac{1}{y^{p_{1}}}-\frac{1}{x^{p_{1}}} \biggr)^{2}+ \mu r(1-r) \biggl(\frac{1}{w^{p_{2}}}-\frac{1}{u^{p_{2}}} \biggr)^{2}, \end{aligned}

whenever $$x,y \in [a,b], u,w \in [c,d]$$, and $$t,r \in [0,1]$$.

VI. If we take $$\Delta (x,y)= -t(1-t) ( \frac{x^{p_{1}}y^{p_{1}}}{x^{p_{1}}-y^{p_{1}}} )^{2}$$ and $$\Delta (u,w)= -r(1-r) ( \frac{u^{p_{2}}w^{p_{2}}}{u^{p_{2}}-w^{p_{2}}} )^{2}$$ in Definition 1, we have a new definition of two-dimensional strongly F harmonic $$(p_{1},h_{1})$$-$$(p_{2},h_{2})$$-convex function.

### Definition 7

Consider the rectangle $$\Omega = [a,b]\times [c,d]\subset (0,\infty )\times (0,\infty )$$. A function $$f: \Omega \rightarrow \mathbb{R}$$ is said to be a two-dimensional strongly F harmonic $$(p_{1},h_{1})$$-$$(p_{2},h_{2})$$-convex function if

\begin{aligned} &f \biggl( \biggl[\frac{x^{p_{1}}y^{p_{1}}}{tx^{p_{1}}+(1-t)y^{p_{1}}} \biggr]^{\frac{1}{p_{1}}}, \biggl[ \frac{u^{p_{2}}w^{p_{2}}}{ru^{p_{2}}+(1-r)w^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}} \biggr) \\ &\quad\leq h_{1}(t)h_{2}(r) f(y,w)+h_{1}(t)h_{2}(1-r) f(y,u)\\ &\qquad{}+h_{1}(1-t)h_{2}(r )f(x,w)+h_{1}(1-t)h_{2}(1-r) f(x,u) \\ &\qquad{}-t(1-t) \biggl(\frac{x^{p_{1}}y^{p_{1}}}{x^{p_{1}}-y^{p_{1}}} \biggr)^{2}- r(1-r) \biggl( \frac{u^{p_{2}}w^{p_{2}}}{u^{p_{2}}-w^{p_{2}}} \biggr)^{2}, \end{aligned}

whenever $$x,y \in [a,b], u,w \in [c,d]$$, and $$t,r \in [0,1]$$.

## 3 Main results

In this section, we discuss our main results.

### Theorem 1

Let $$f: \Omega \rightarrow \mathbb{R}$$ be an integrable function. If f is an approximately two-dimensional harmonically $$(p_{1},h_{1})$$-$$(p_{2},h_{2})$$-convex function, then

\begin{aligned} &\frac{1}{4h_{1}({\frac{1}{2}})h_{2}({\frac{1}{2}})} \biggl[f \biggl( \biggl[\frac{2a^{p_{1}}b^{p_{1}}}{a^{p_{1}}+b^{p_{1}}} \biggr]^{ \frac{1}{p_{1}}}, \biggl[ \frac{2c^{p_{2}}d^{p_{2}}}{c^{p_{2}}+d^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}} \biggr)\\ &\qquad{}- \frac{p_{1}a^{p_{1}}b^{p_{1}}}{b^{p_{1}}-a^{p_{1}}} \int _{a}^{b} \frac{\Delta (x, ((a^{p_{1}})^{-1}+(b^{p_{1}})^{-1}-(x^{p_{1}})^{-1})^{-1})}{x^{1+p_{1}}} \,\mathrm{d}x \\ &\qquad{} -\frac{p_{2}c^{p_{2}}d^{p_{2}}}{d^{p_{2}}-c^{p_{2}}} \int _{c}^{d} \frac{\Delta (u, ((c^{p_{2}})^{-1}+(d^{p_{2}})^{-1}-(u^{p_{2}})^{-1})^{-1})}{u^{1+p_{2}}} \,\mathrm{d}u \biggr] \\ &\quad\leq p_{1}p_{2} \biggl(\frac{a^{p_{1}}b^{p_{1}}}{b^{p_{1}}-a^{p_{1}}} \biggr) \biggl( \frac{c^{p_{2}}d^{p_{2}}}{d^{p_{2}}-c^{p_{2}}} \biggr) \int _{a}^{b} \int _{c}^{d} \frac{f(x,u)}{x^{1+p_{1}}u^{1+p_{2}}}\,\mathrm{d}u\, \mathrm{d}x \\ &\quad\leq \bigl[f(a,c)+f(a,d)+f(b,c)+f(b,d) \bigr] \int _{0}^{1} \int _{0}^{1}h_{1}(t)h_{2}(r) \,\mathrm{d}t\,\mathrm{d}r+\Delta (a,b)+ \Delta (c,d). \end{aligned}

### Proof

Since f is an approximately two-dimensional harmonic $$(p_{1},h_{1})$$-$$(p_{2},h_{2})$$-convex function, we have

\begin{aligned} &f \biggl( \biggl[\frac{2a^{p_{1}}b^{p_{1}}}{a^{p_{1}}+b^{p_{1}}} \biggr]^{ \frac{1}{p_{1}}}, \biggl[ \frac{2c^{p_{2}}d^{p_{2}}}{c^{p_{2}}+d^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}} \biggr) \\ &\quad\leq h_{1} \biggl(\frac{1}{2} \biggr)h_{2} \biggl( \frac{1}{2} \biggr) \\ &\qquad{}\times \biggl[f \biggl( \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{ta^{p_{1}}+(1-t)b^{p_{1}}} \biggr]^{ \frac{1}{p_{1}}}, \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{rc^{p_{2}}+(1-r)d^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}} \biggr)\\ &\qquad{}+f \biggl( \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{ta^{p_{1}}+(1-t)b^{p_{1}}} \biggr]^{ \frac{1}{p_{1}}}, \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{rd^{p_{2}}+(1-r)c^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}} \biggr) \\ &\qquad{} +f \biggl( \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{tb^{p_{1}}+(1-t)a^{p_{1}}} \biggr]^{ \frac{1}{p_{1}}}, \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{rc^{p_{2}}+(1-r)d^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}} \biggr)\\ &\qquad{}+f \biggl( \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{tb^{p_{1}}+(1-t)a^{p_{1}}} \biggr]^{ \frac{1}{p_{1}}}, \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{rd^{p_{2}}+(1-r)c^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}} \biggr] \biggr) \\ & \qquad{}+\Delta \biggl( \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{ta^{p_{1}}+(1-t)b^{p_{1}}} \biggr]^{ \frac{1}{p_{1}}}, \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{tb^{p_{1}}+(1-t)a^{p_{1}}} \biggr]^{ \frac{1}{p_{1}}} \biggr) \\ &\qquad{}+\Delta \biggl( \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{rc^{p_{2}}+(1-r)d^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}}, \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{rd^{p_{2}}+(1-r)c^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}} \biggr) ]. \end{aligned}

Integrating the above inequality with respect to $$(t,r)$$ on $$[0,1]\times [0,1]$$, we have

\begin{aligned} &\frac{1}{4h_{1} (\frac{1}{2} )h_{2} (\frac{1}{2} )} \biggl[f \biggl( \biggl[\frac{2a^{p_{1}}b^{p_{1}}}{a^{p_{1}}+b^{p_{1}}} \biggr]^{\frac{1}{p_{1}}}, \biggl[ \frac{2c^{p_{2}}d^{p_{2}}}{c^{p_{2}}+d^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}} \biggr)\\ &\qquad{}- \frac{p_{1}a^{p_{1}}b^{p_{1}}}{b^{p_{1}}-a^{p_{1}}} \int _{a}^{b} \frac{\Delta (x,((a^{p_{1}})^{-1}+(b^{p_{1}})^{-1}-(x^{p_{1}})^{-1})^{-1})}{x^{1+p_{1}}} \,\mathrm{d}x \\ &\qquad{} -\frac{p_{2}c^{p_{2}}d^{p_{2}}}{d^{p_{2}}-c^{p_{2}}} \int _{c}^{d} \frac{\Delta (u,((c^{p_{2}})^{-1}+(d^{p_{2}})^{-1}-(u^{p_{2}})^{-1})^{-1})}{u^{1+p_{2}}} \,\mathrm{d}u \biggr] \\ &\quad\leq p_{1}p_{2} \biggl(\frac{a^{p_{1}}b^{p_{1}}}{b^{p_{1}}-a^{p_{1}}} \biggr) \biggl( \frac{c^{p_{2}}d^{p_{2}}}{d^{p_{2}}-c^{p_{2}}} \biggr) \int _{a}^{b} \int _{c}^{d} \frac{f(x,u)}{x^{1+p_{1}}u^{1+p_{2}}}\,\mathrm{d}u\, \mathrm{d}x. \end{aligned}

Also

\begin{aligned} &f \biggl( \biggl[\frac{a^{p_{1}}b^{p_{1}}}{ta^{p_{1}}+(1-t)b^{p_{1}}} \biggr]^{\frac{1}{p_{1}}}, \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{rc^{p_{2}}+(1-r)d^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}} \biggr) \\ &\quad\leq h_{1}(t)h_{2}(r) f(b,d)+h_{1}(t)h_{2}(1-r) f(b,c)+h_{1}(1-t)h_{2}(r )f(a,d) \\ &\qquad{} +h_{1}(1-t)h_{2}(1-r) f(a,c)+\Delta (a,b)+\Delta (c,d). \end{aligned}

Integrating both sides of the above inequality with respect to $$(t,r)$$ on $$[0,1]\times [0,1]$$, we have

\begin{aligned} &p_{1}p_{2} \biggl(\frac{a^{p_{1}}b^{p_{1}}}{b^{p_{1}}-a^{p_{1}}} \biggr) \biggl( \frac{c^{p_{2}}d^{p_{2}}}{d^{p_{2}}-c^{p_{2}}} \biggr) \int _{a}^{b} \int _{c}^{d} \frac{f(x,u)}{x^{1+p_{1}}u^{1+p_{2}}}\,\mathrm{d}u\, \mathrm{d}x \\ &\quad\leq \bigl(f(a,c)+f(a,d)+f(b,c)+f(b,d) \bigr) \int _{0}^{1} \int _{0}^{1}h_{1}(t)h_{2}(r) \,\mathrm{d}t\,\mathrm{d}r+\Delta (a,b)+ \Delta (c,d). \end{aligned}

This completes the proof. □

We now discuss some special cases of Theorem 1.

I. If $$h_{1}(t)=t$$ and $$h_{2}(r)=r$$ in Theorem 1, then

### Corollary 1

Under the assumptions of Theorem 1, if f is an approximately two-dimensional harmonic $$(p_{1}, p_{2})$$-convex function, then

\begin{aligned} &f \biggl( \biggl[\frac{2a^{p_{1}}b^{p_{1}}}{a^{p_{1}}+b^{p_{1}}} \biggr]^{ \frac{1}{p_{1}}}, \biggl[ \frac{2c^{p_{2}}d^{p_{2}}}{c^{p_{2}}+d^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}} \biggr)\\ &\qquad{}- \frac{p_{1}a^{p_{1}}b^{p_{1}}}{b^{p_{1}}-a^{p_{1}}} \int _{a}^{b} \frac{\Delta (x, ((a^{p_{1}})^{-1}+(b^{p_{1}})^{-1}-(x^{p_{1}})^{-1})^{-1})}{x^{1+p_{1}}} \,\mathrm{d}x \\ &\qquad{}-\frac{p_{2}c^{p_{2}}d^{p_{2}}}{d^{p_{2}}-c^{p_{2}}} \int _{c}^{d} \frac{\Delta (u, ((c^{p_{2}})^{-1}+(d^{p_{2}})^{-1}-(u^{p_{2}})^{-1})^{-1})}{u^{1+p_{2}}} \,\mathrm{d}u \\ &\quad\leq p_{1}p_{2} \biggl(\frac{a^{p_{1}}b^{p_{1}}}{b^{p_{1}}-a^{p_{1}}} \biggr) \biggl( \frac{c^{p_{2}}d^{p_{2}}}{d^{p_{2}}-c^{p_{2}}} \biggr) \int _{a}^{b} \int _{c}^{d} \frac{f(x,u)}{x^{1+p_{1}}u^{1+p_{2}}}\,\mathrm{d}u\, \mathrm{d}x \\ &\quad\leq \frac{ [f(a,c)+f(a,d)+f(b,c)+f(b,d) ]}{4}+\Delta (a,b)+ \Delta (c,d). \end{aligned}

II. If $$h_{1}(t)=t^{s_{1}}$$ and $$h(r)=r^{s_{2}}$$ in Theorem 1, then

### Corollary 2

Under the assumptions of Theorem 1, if f is a Breckner type approximately two-dimensional harmonic $$(p_{1},s_{1})$$-$$(p_{2},s_{2})$$-convex function, then

\begin{aligned} &\frac{2^{s_{1}+s_{2}}}{4} \biggl[f \biggl( \biggl[ \frac{2a^{p_{1}}b^{p_{1}}}{a^{p_{1}}+b^{p_{1}}} \biggr]^{ \frac{1}{p_{1}}}, \biggl[ \frac{2c^{p_{2}}d^{p_{2}}}{c^{p_{2}}+d^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}} \biggr)\\ &\qquad{}- \frac{p_{1}a^{p_{1}}b^{p_{1}}}{b^{p_{1}}-a^{p_{1}}} \int _{a}^{b} \frac{\Delta (x, ((a^{p_{1}})^{-1}+(b^{p_{1}})^{-1}-(x^{p_{1}})^{-1})^{-1})}{x^{1+p_{1}}} \,\mathrm{d}x \\ &\qquad{} -\frac{p_{2}c^{p_{2}}d^{p_{2}}}{d^{p_{2}}-c^{p_{2}}} \int _{c}^{d} \frac{\Delta (u, ((c^{p_{2}})^{-1}+(d^{p_{2}})^{-1}-(u^{p_{2}})^{-1})^{-1})}{u^{1+p_{2}}} \,\mathrm{d}u \biggr] \\ &\quad\leq p_{1}p_{2} \biggl(\frac{a^{p_{1}}b^{p_{1}}}{b^{p_{1}}-a^{p_{1}}} \biggr) \biggl( \frac{c^{p_{2}}d^{p_{2}}}{d^{p_{2}}-c^{p_{2}}} \biggr) \int _{a}^{b} \int _{c}^{d} \frac{f(x,u)}{x^{1+p_{1}}u^{1+p_{2}}}\,\mathrm{d}u\, \mathrm{d}x \\ &\quad\leq \frac{f(a,c)+f(a,d)+f(b,c)+f(b,d)}{(s_{1}+1)(s_{2}+1)}+\Delta (a,b)+ \Delta (c,d). \end{aligned}

III. If $$h_{1}(t)=t^{-s_{1}}$$ and $$h_{2}(r)=r^{-s_{2}}$$ in Theorem 1, then

### Corollary 3

Under the assumptions of Theorem 1, if f is a Godunova–Levin type approximately two-dimensional harmonic $$(p_{1},s_{1})$$-$$(p_{2},s_{2})$$-convex function, then

\begin{aligned} &\frac{1}{4.2^{s_{1}+s_{2}}} \biggl[f \biggl( \biggl[ \frac{2a^{p_{1}}b^{p_{1}}}{a^{p_{1}}+b^{p_{1}}} \biggr]^{ \frac{1}{p_{1}}}, \biggl[ \frac{2c^{p_{2}}d^{p_{2}}}{c^{p_{2}}+d^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}} \biggr)\\ &\qquad{}- \frac{p_{1}a^{p_{1}}b^{p_{1}}}{b^{p_{1}}-a^{p_{1}}} \int _{a}^{b} \frac{\Delta (x, ((a^{p_{1}})^{-1}+(b^{p_{1}})^{-1}-(x^{p_{1}})^{-1})^{-1})}{x^{1+p_{1}}} \,\mathrm{d}x \\ & \qquad{}-\frac{p_{2}c^{p_{2}}d^{p_{2}}}{d^{p_{2}}-c^{p_{2}}} \int _{c}^{d} \frac{\Delta (u, ((c^{p_{2}})^{-1}+(d^{p_{2}})^{-1}-(u^{p_{2}})^{-1})^{-1})}{u^{1+p_{2}}} \,\mathrm{d}u \biggr] \\ &\quad\leq p_{1}p_{2} \biggl(\frac{a^{p_{1}}b^{p_{1}}}{b^{p_{1}}-a^{p_{1}}} \biggr) \biggl( \frac{c^{p_{2}}d^{p_{2}}}{d^{p_{2}}-c^{p_{2}}} \biggr) \int _{a}^{b} \int _{c}^{d} \frac{f(x,u)}{x^{1+p_{1}}u^{1+p_{2}}}\,\mathrm{d}u\, \mathrm{d}x \\ &\quad\leq \frac{f(a,c)+f(a,d)+f(b,c)+f(b,d)}{(1-s_{1})(1-s_{2})}+\Delta (a,b)+ \Delta (c,d). \end{aligned}

IV. If $$h_{1}(t)=1$$ and $$h_{2}(r)=1$$ in Theorem 1, then

### Corollary 4

Under the assumptions of Theorem 1, if f is an approximately two-dimensional harmonic $$(p_{1}, P)$$-$$(p_{2},P)$$-convex function, then

\begin{aligned} &\frac{1}{4} \biggl[f \biggl( \biggl[ \frac{2a^{p_{1}}b^{p_{1}}}{a^{p_{1}}+b^{p_{1}}} \biggr]^{ \frac{1}{p_{1}}}, \biggl[ \frac{2c^{p_{2}}d^{p_{2}}}{c^{p_{2}}+d^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}} \biggr)\\ &\qquad{}- \frac{p_{1}a^{p_{1}}b^{p_{1}}}{b^{p_{1}}-a^{p_{1}}} \int _{a}^{b} \frac{\Delta (x, ((a^{p_{1}})^{-1}+(b^{p_{1}})^{-1}-(x^{p_{1}})^{-1})^{-1})}{x^{1+p_{1}}} \,\mathrm{d}x \\ &\qquad{} -\frac{p_{2}c^{p_{2}}d^{p_{2}}}{d^{p_{2}}-c^{p_{2}}} \int _{c}^{d} \frac{\Delta (u, ((c^{p_{2}})^{-1}+(d^{p_{2}})^{-1}-(u^{p_{2}})^{-1})^{-1})}{u^{1+p_{2}}} \,\mathrm{d}u \biggr] \\ &\quad\leq p_{1}p_{2} \biggl(\frac{a^{p_{1}}b^{p_{1}}}{b^{p_{1}}-a^{p_{1}}} \biggr) \biggl( \frac{c^{p_{2}}d^{p_{2}}}{d^{p_{2}}-c^{p_{2}}} \biggr) \int _{a}^{b} \int _{c}^{d} \frac{f(x,u)}{x^{1+p_{1}}u^{1+p_{2}}}\,\mathrm{d}u\, \mathrm{d}x \\ &\quad\leq \bigl[f(a,c)+f(a,d)+f(b,c)+f(b,d)\bigr]+\Delta (a,b)+\Delta (c,d). \end{aligned}

Now we introduce a generalized identity that will play a significant role in the development of our next results.

### Lemma 1

Let $$f:\Omega \rightarrow \mathbb{R}$$ be a partial differential function on $$\Omega =[a,b]\times [c,d]\subset (0,\infty )\times (0,\infty )$$ with $$a^{p_{1}}< b^{p_{1}}$$ and $$c^{p_{2}}< d^{p_{2}}$$. If $$\frac{\partial ^{2}f}{\partial t\, \partial r}\in L_{1}(\Omega )$$, then

\begin{aligned} &\Xi \bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}},x,y: \Omega \bigr) \\ &\quad= \frac{(b^{p_{1}}-a^{p_{1}})(d^{p_{2}}-c^{p_{2}})}{4p_{1}p_{2}a^{p_{1}}b^{p_{1}}c^{p_{2}}d^{p_{2}}} \int _{0}^{1} \int _{0}^{1} \biggl((1-2t) \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr)\\ &\qquad{}\times \biggl((1-2r) \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr) \\ &\qquad{} \times \frac{\partial ^{2}f}{\partial r\, \partial t} \biggl( \biggl[\frac{a^{p_{1}}b^{p_{1}}}{tb^{p_{1}}+(1-t)a^{p_{1}}} \biggr]^{ \frac{1}{p_{1}}}, \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{rd^{p_{2}}+(1-r)c^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}} \biggr)\, \mathrm{d}r\,\mathrm{d}t, \end{aligned}

where

\begin{aligned} &\Xi \bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}},x,y: \Omega \bigr) \\ &\quad=\frac{f(a,c)+f(b,c)+f(a,d)+f(b,d)}{4} -\frac{1}{2} \biggl[ \frac{p_{1}a^{p_{1}}b^{p_{1}}}{b^{p_{1}}-a^{p_{1}}} \biggl[ \int _{a}^{b}\frac{f(x,c)}{x^{1+p_{1}}}\,\mathrm{d}x+ \int _{a}^{b} \frac{f(x,d)}{x^{1+p_{1}}}\,\mathrm{d}x \biggr] \\ &\qquad{}+\frac{p_{2}c^{p_{2}}d^{p_{2}}}{d^{p_{2}}-c^{p_{2}}} \biggl[ \int _{c}^{d}\frac{f(a,u)}{u^{1+p_{2}}}\,\mathrm{d}u+ \int _{c}^{d} \frac{f(b,u)}{u^{1+p_{2}}}\,\mathrm{d}u \biggr] \biggr] \\ &\qquad{}+ \frac{p_{1}p_{2}a^{p_{1}}b^{p_{1}}c^{p_{2}}d^{p_{2}}}{(b^{p_{1}}-a^{p_{1}})(d^{p_{2}}-c^{p_{2}})} \int _{a}^{b} \int _{c}^{d} \frac{f(x,u)}{x^{1+p_{1}}u^{1+p_{2}}}\,\mathrm{d}u\, \mathrm{d}x. \end{aligned}

### Proof

It suffices to note that we can write

\begin{aligned} &\Xi \bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}},x,y: \Omega \bigr) \\ &\quad= \frac{(b^{p_{1}}-a^{p_{1}})(d^{p_{2}}-c^{p_{2}})}{4p_{1}p_{2}a^{p_{1}}b^{p_{1}}c^{p_{2}}d^{p_{2}}} \int _{0}^{1} \biggl((1-2t) \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr) \\ &\qquad{}\times \biggl[ \int _{0}^{1} \biggl((1-2r) \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr)\\ &\qquad{}\times\frac{\partial ^{2}f}{\partial r\, \partial t} \biggl( \biggl[\frac{a^{p_{1}}b^{p_{1}}}{tb^{p_{1}}+(1-t)a^{p_{1}}} \biggr]^{ \frac{1}{p_{1}}}, \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{rd^{p_{2}}+(1-r)c^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}} \biggr)\,\mathrm{d}r \biggr]\,\mathrm{d}t. \end{aligned}

Now, integrating by parts, we have

\begin{aligned} I_{1}={}& \int _{0}^{1} \biggl( (1-2r) \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr) \\ &{}\times\frac{\partial ^{2}f}{\partial r\, \partial t} \biggl( \biggl[\frac{a^{p_{1}}b^{p_{1}}}{tb^{p_{1}}+(1-t)a^{p_{1}}} \biggr]^{ \frac{1}{p_{1}}}, \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{rd^{p_{2}}+(1-r)c^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}} \biggr)\,\mathrm{d}r \\ = {}&\frac{p_{2}c^{p_{2}}d^{p_{2}}}{ ( d^{p_{2}}-c^{p_{2}} ) } \frac{\partial f}{\partial t} \biggl( \frac{a^{p_{1}}b^{p_{1}}}{tb^{p_{1}}+(1-t)a^{p_{1}}} ]^{ \frac{1}{p_{1}}},c \biggr) + \frac{p_{2}c^{p_{2}}d^{p_{2}}}{ ( d^{p_{2}}-c^{p_{2}} ) } \frac{\partial f}{\partial t} \biggl( \frac{a^{p_{1}}b^{p_{1}}}{tb^{p_{1}}+(1-t)a^{p_{1}}} ]^{ \frac{1}{p_{1}}},d \biggr) \\ &{} - \frac{2p_{2}c^{p_{2}}d^{p_{2}}}{ ( d^{p_{2}}-c^{p_{2}} ) } \int _{0}^{1} \frac{\partial f}{\partial t} \biggl( \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{tb^{p_{1}}+(1-t)a^{p_{1}}} \biggr]^{ \frac{1}{p_{1}}}, \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{rd^{p_{2}}+(1-r)c^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}} \biggr) \,\mathrm{d}r, \\ I_{2}={}& \int _{0}^{1} \biggl((1-2t) \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr) \frac{\partial f}{\partial t} \biggl( \frac{a^{p_{1}}b^{p_{1}}}{tb^{p_{1}}+(1-t)a^{p_{1}}} ]^{ \frac{1}{p_{1}}},c \biggr) \,\mathrm{d}t \\ = {}&\frac{p_{1}a^{p}_{1}b^{p}_{1}}{ ( b^{p_{1}}-a^{p_{1}} ) } \bigl\{ f ( a,c ) +f ( b,c ) \bigr\} - \frac{2p_{1}^{2}(a^{p}_{1}b^{p}_{1})^{2}}{ ( b^{p_{1}}-a^{p_{1}} ) ^{2}} \int _{a}^{b}\frac{f ( x,c ) }{x^{1+p_{1}}}\,\mathrm{d}x, \\ I_{3}={}& \int _{0}^{1} \biggl((1-2t) \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr) \frac{\partial f}{\partial t} \biggl( \frac{a^{p_{1}}b^{p_{1}}}{tb^{p_{1}}+(1-t)a^{p_{1}}} ]^{ \frac{1}{p_{1}}},d \biggr) \,\mathrm{d}t \\ = {}&\frac{p_{1}a^{p}_{1}b^{p}_{1}}{ ( b^{p_{1}}-a^{p_{1}} ) } \bigl\{ f ( a,d ) +f ( b,d ) \bigr\} - \frac{2p_{1}^{2}(a^{p}_{1}b^{p}_{1})^{2}}{ ( b^{p_{1}}-a^{p_{1}} ) ^{2}} \int _{a}^{b}\frac{f ( x,d ) }{x^{1+p_{1}}}\,\mathrm{d}x, \\ I_{4}={}& \int _{0}^{1} \biggl\{ \int _{0}^{1} \biggl( (1-2t) \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr)\\ &{}\times\frac{\partial f}{\partial t} \biggl( \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{tb^{p_{1}}+(1-t)a^{p_{1}}} \biggr]^{ \frac{1}{p_{1}}}, \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{rd^{p_{2}}+(1-r)c^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}} \biggr) \,\mathrm{d}t \biggr\} \,\mathrm{d}r \\ ={}&\frac{\{f(a,c)+f(b,c)+f(a,d)+f(b,d)\}}{4}-\frac{1}{2} \biggl[ \frac{p_{1}a^{p}_{1}b^{p}_{1}}{b^{p_{1}}-a^{p_{1}}} \biggl\{ \int _{a}^{b}\frac{f(x,c)}{x^{1+p_{1}}} \,\mathrm{d}x+ \int _{a}^{b}\frac{f(x,d)}{x^{1+p_{1}}}\,\mathrm{d}x \biggr\} \\ &{} +\frac{p_{2}c^{p_{2}}d^{p_{2}}}{d^{p_{2}}-c^{p_{2}}} \biggl\{ \int _{c}^{d}\frac{f(a,u)}{u^{1+p_{2}}} \,\mathrm{d}u+ \int _{c}^{d}\frac{f(b,u)}{u^{1+p_{2}}}\,\mathrm{d}u \biggr\} \biggr]\\ &{}+ \frac{p_{1}p_{2}(a^{p}_{1}b^{p}_{1}a^{p}_{1}b^{p}_{1})}{ ( b^{p_{1}}-a^{p_{1}} ) ( d^{p_{2}}-c^{p_{2}} ) } \int _{a}^{b} \int _{c}^{d} \frac{f ( x,u ) }{x^{1+p_{1}}u^{1+p_{2}}}\,\mathrm{d}x \, \mathrm{d}u. \end{aligned}

Summing up integrals $$I_{1}$$ to $$I_{4}$$ and using the change of variable technique will give the required result. □

### Remark 1

Letting $$p_{1}=1=p_{2}$$ in the above lemma, we get the lemma proved in [4].

In order to obtain next results, we need gamma, beta, and hypergeometric functions. Gamma $$\Gamma (\cdot)$$ and beta function $$B(\cdot,\cdot)$$ are defined respectively as follows:

\begin{aligned} &\Gamma (x)= \int _{0}^{\infty }e^{-x}t^{x-1}\, \mathrm{d}t, \\ &\mathrm{B}(x,y)=\frac{\Gamma (x)\Gamma (y)}{\Gamma (x+y)}= \int _{0}^{1}t^{x-1}(1-t)^{y-1} \,\mathrm{d}t. \end{aligned}

The integral form of the hypergeometric function is

$$_{2}F_{1}(x,y;c;z)=\frac{1}{\mathrm{B}(y,c-y)}\int _{0}^{1}t^{y-1}(1-t)^{c-y-1}(1-zt)^{-x} \,\mathrm{d}t$$

for $$|z|<1,c>y>0$$. Now, using Lemma 1, we prove the next results of the article.

### Theorem 2

Let $$f:\Omega \rightarrow \mathbb{R}$$ be a partial differentiable function on $$\Omega = [a,b]\times [c,d]\subset (0,\infty )\times (0,\infty )$$ with $$a^{p_{1}}< b^{p_{1}}$$ and $$c^{p_{2}}< d^{p_{2}}$$ and $$\frac{\partial ^{2}f}{\partial t\, \partial r}\in L_{1}(\Omega )$$. If $$|\frac{\partial ^{2}f}{\partial r \,\partial t} |$$ is an approximately two-dimensional harmonic $$(p_{1},h_{1})$$-$$(p_{2},h_{2})$$-convex function, then

\begin{aligned} & \bigl\vert \Xi \bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}},x,y: \Omega \bigr) \bigr\vert \\ &\quad\leq \frac{(b^{p_{1}}-a^{p_{1}})(d^{p_{2}}-c^{p_{2}})}{4p_{1}p_{2}a^{p_{1}}b^{p_{1}}c^{p_{2}}d^{p_{2}}} \biggl[\vartheta _{1}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,c) \biggr\vert \\ &\qquad{} +\vartheta _{2}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,c) \biggr\vert + \vartheta _{3}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,d) \biggr\vert \\ & \qquad{}+\vartheta _{4}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,d) \biggr\vert + \vartheta _{5}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr)\\ &\qquad{}+ \vartheta _{6}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggr], \end{aligned}

where

\begin{aligned} &\vartheta _{1}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[ \vert 1-2t \vert h_{1}(t) \biggl[\frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr]\\ &\qquad{}\times \biggl[ \vert 1-2r \vert h_{2}(r) \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr]\,\mathrm{d}t\,\mathrm{d}r, \\ &\vartheta _{2}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[ \vert 1-2t \vert h_{1}(1-t) \biggl[\frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr]\\ &\qquad{}\times \biggl[ \vert 1-2r \vert h_{2}(r) \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr]\,\mathrm{d}t\,\mathrm{d}r, \\ &\vartheta _{3}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[ \vert 1-2t \vert h_{1}(t) \biggl[\frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr]\\ &\qquad{}\times \biggl[ \vert 1-2r \vert h_{2}(1-r) \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr]\,\mathrm{d}t\,\mathrm{d}r, \\ &\vartheta _{4}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[ \vert 1-2t \vert h_{1}(1-t) \biggl[\frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr]\\ &\qquad{}\times \biggl[ \vert 1-2r \vert h_{2}(1-r) \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr]\,\mathrm{d}t\,\mathrm{d}r, \\ &\vartheta _{5}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \\ &\quad=\Delta (a,b) \int _{0}^{1} \int _{0}^{1} \biggl[ \vert 1-2t \vert \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr]\\ &\qquad{}\times \biggl[ \vert 1-2r \vert \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr]\,\mathrm{d}t\,\mathrm{d}r \\ &\quad=\Delta (a,b) \biggl[ \bigl(b^{p_{1}}\bigr)^{1+\frac{1}{p_{1}}} {}_{2}F_{1} \biggl(1+\frac{1}{p_{1}},2,3,1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr)\\ &\qquad{}- \bigl(b^{p_{1}}\bigr)^{1+ \frac{1}{p_{1}}} {}_{2}F_{1} \biggl(1+\frac{1}{p_{1}},1,2,1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \\ &\qquad{}+\frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{2} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},1,3,\frac{1}{2} \biggl(1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr) \biggr] \\ &\qquad{}\times\biggl[ \bigl(d^{p_{2}}\bigr)^{1+\frac{1}{p_{2}}} {}_{2}F_{1} \biggl(1+\frac{1}{p_{2}},2,3,1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \\ &\qquad{}-\bigl(d^{p_{2}}\bigr)^{1+\frac{1}{p_{2}}} {}_{2}F_{1} \biggl(1+\frac{1}{p_{2}},1,2,1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr)\\ &\qquad{}+ \frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{2} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},1,3, \frac{1}{2} \biggl(1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr) \biggr], \end{aligned}

and

\begin{aligned} &\vartheta _{6}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \\ &\quad=\Delta (c,d) \int _{0}^{1} \int _{0}^{1} \biggl[ \vert 1-2t \vert \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr] \\ &\qquad{}\times\biggl[ \vert 1-2r \vert \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr]\,\mathrm{d}t\, \mathrm{d}r \\ &\quad=\Delta (c,d) \biggl[ \bigl(b^{p_{1}}\bigr)^{1+\frac{1}{p_{1}}} {}_{2}F_{1} \biggl(1+\frac{1}{p_{1}},2,3,1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr)- \bigl(b^{p_{1}}\bigr)^{1+ \frac{1}{p_{1}}} {}_{2}F_{1} \biggl(1+\frac{1}{p_{1}},1,2,1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \\ &\qquad{}+\frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{2} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},1,3,\frac{1}{2} \biggl(1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr) \biggr] \biggl[ \bigl(d^{p_{2}}\bigr)^{1+\frac{1}{p_{2}}} {}_{2}F_{1} \biggl(1+\frac{1}{p_{2}},2,3,1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \\ &\qquad{}-\bigl(d^{p_{2}}\bigr)^{1+\frac{1}{p_{2}}} {}_{2}F_{1} \biggl(1+\frac{1}{p_{2}},1,2,1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr)\\ &\qquad{}+ \frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{2} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},1,3, \frac{1}{2} \biggl(1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr) \biggr]. \end{aligned}

### Proof

Using Lemma 1 and the fact that $$|\frac{\partial ^{2}f}{\partial r \,\partial t} |$$ is an approximately two-dimensional harmonic $$(p_{1},h_{1})$$-$$(p_{2},h_{2})$$-convex function, then

\begin{aligned} & \bigl\vert \Xi \bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}},x,y: \Omega \bigr) \bigr\vert \\ &\quad= \biggl\vert \frac{(b^{p_{1}}-a^{p_{1}})(d^{p_{2}}-c^{p_{2}})}{4p_{1}p_{2}a^{p_{1}}b^{p_{1}}c^{p_{2}}d^{p_{2}}} \int _{0}^{1} \int _{0}^{1} \biggl((1-2t) \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr) \\ &\qquad{}\times\biggl((1-2r) \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr) \\ &\qquad{} \times \frac{\partial ^{2}f}{\partial r \,\partial t} \biggl( \biggl[\frac{a^{p_{1}}b^{p_{1}}}{tb^{p_{1}}+(1-t)a^{p_{1}}} \biggr]^{ \frac{1}{p_{1}}}, \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{rd^{p_{2}}+(1-r)c^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}} \biggr)\, \mathrm{d}r\,\mathrm{d}t \biggr\vert \\ &\quad\leq \frac{(b^{p_{1}}-a^{p_{1}})(d^{p_{2}}-c^{p_{2}})}{4p_{1}p_{2}a^{p_{1}}b^{p_{1}}c^{p_{2}}d^{p_{2}}} \int _{0}^{1} \int _{0}^{1} \biggl[ \vert 1-2t \vert \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr] \\ &\qquad{}\times\biggl[ \vert 1-2r \vert \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr] \\ &\qquad{} \times \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t} \biggl( \biggl[\frac{a^{p_{1}}b^{p_{1}}}{tb^{p_{1}}+(1-t)a^{p_{1}}} \biggr]^{ \frac{1}{p_{1}}}, \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{rd^{p_{2}}+(1-r)c^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}} \biggr) \biggr\vert \,\mathrm{d}r\,\mathrm{d}t \\ &\quad\leq \frac{(b^{p_{1}}-a^{p_{1}})(d^{p_{2}}-c^{p_{2}})}{4p_{1}p_{2}a^{p_{1}}b^{p_{1}}c^{p_{2}}d^{p_{2}}} \int _{0}^{1} \int _{0}^{1} \biggl[ \vert 1-2t \vert \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr]\\ &\qquad{}\times \biggl[ \vert 1-2r \vert \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr] \\ &\qquad{} \times \biggl[h_{1}(t)h_{2}(r) \biggl\vert \frac{\partial ^{2}f}{\partial r\, \partial t}(a,c) \biggr\vert +h_{1}(1-t)h_{2}(r) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,c) \biggr\vert \\ &\qquad{}+h_{1}(t)h_{2}(1-r) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,d) \biggr\vert \\ &\qquad{} +h_{1}(1-t)h_{2}(1-r) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,d) \biggr\vert +\Delta (a,b)+ \Delta (c,d) \biggr]\, \mathrm{d}r\,\mathrm{d}t. \end{aligned}

This completes the proof. □

### Corollary 5

Under the assumptions of Theorem 2, if $$|\frac{\partial ^{2}f}{\partial r \,\partial t} |\le M$$ is a bounded function for $$M>0$$ on Ω, then

\begin{aligned} & \bigl\vert \Xi \bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}},x,y: \Omega \bigr) \bigr\vert \\ &\quad\leq \frac{M(b^{p_{1}}-a^{p_{1}})(d^{p_{2}}-c^{p_{2}})}{4p_{1}p_{2}a^{p_{1}}b^{p_{1}}c^{p_{2}}d^{p_{2}}} \biggl[\vartheta _{1}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \\ &\qquad{} +\vartheta _{2}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr)+\vartheta _{3}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \\ &\qquad{} +\vartheta _{4}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr)+\frac{1}{M}\vartheta _{5}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr)\\ &\qquad{}+\frac{1}{M}\vartheta _{6}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggr], \end{aligned}

where $$\vartheta _{1}(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}:\Omega )$$ to $$\vartheta _{6}(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}:\Omega )$$ are given in Theorem 2.

We now discuss some special cases of Theorem 2.

I. If we take $$h_{1}(t)=t$$ and $$h_{2}(r)=r$$ in Theorem 2, then

### Corollary 6

Under the assumptions of Theorem 2, if $$|\frac{\partial ^{2}f}{\partial r \,\partial t} |$$ is an approximately two-dimensional harmonic $$(p_{1},p_{2})$$-convex function, then

\begin{aligned} & \bigl\vert \Xi \bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}},x,y: \Omega \bigr) \bigr\vert \\ &\quad\leq \frac{(b^{p_{1}}-a^{p_{1}})(d^{p_{2}}-c^{p_{2}})}{4p_{1}p_{2}a^{p_{1}}b^{p_{1}}c^{p_{2}}d^{p_{2}}} \biggl[\vartheta _{1}^{*} \bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,c) \biggr\vert \\ & \qquad{}+\vartheta _{2}^{*}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,c) \biggr\vert + \vartheta _{3}^{*}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,d) \biggr\vert \\ &\qquad{} +\vartheta _{4}^{*}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,d) \biggr\vert + \vartheta _{5}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr)\\ &\qquad{}+ \vartheta _{6}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggr], \end{aligned}

where

\begin{aligned} &\vartheta _{1}^{*}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[ \vert 1-2t \vert t \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr]\\ &\qquad{}\times \biggl[ \vert 1-2r \vert r \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr]\,\mathrm{d}t\, \mathrm{d}r \\ &\quad= \biggl[\frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{12} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},2,4,\frac{1}{2} \biggl(1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr)+\frac{ 2(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{3} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},3,4,1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \\ &\qquad{}-\frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{2} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},2,3,1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr] \biggl[ \frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{12} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},2,4,\frac{1}{2} \biggl(1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr) \\ &\qquad{}+\frac{ 2(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{3} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},3,4,1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr)- \frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{2} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},2,3,1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr], \\ &\vartheta _{2}^{*}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[ \vert 1-2t \vert (1-t) \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr] \\ &\qquad{}\times\biggl[ \vert 1-2r \vert r \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr]\,\mathrm{d}t\, \mathrm{d}r \\ &\quad= \biggl[\frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{2} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},1,3,\frac{1}{2} \biggl(1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr)\\ &\qquad{} -\frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{12} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},2,4,\frac{1}{2} \biggl(1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr) \\ &\qquad{}+\frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{3} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},2,4,1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr)- \frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{2} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},1,3,1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr] \\ &\qquad{} \times \biggl[\frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{12} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},2,4,\frac{1}{2} \biggl(1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr) \\ &\qquad{}+\frac{ 2(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{3} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},3,4,1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr)- \frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{2} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},2,3,1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr], \\ &\vartheta _{3}^{*}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[ \vert 1-2t \vert t \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr] \\ &\qquad{}\times\biggl[ \vert 1-2r \vert (1-r) \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr]\, \mathrm{d}t\,\mathrm{d}r \\ &\quad= \biggl[\frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{12} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},2,4,\frac{1}{2} \biggl(1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr)+\frac{ 2(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{3} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},3,4,1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \\ &\qquad{}-\frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{2} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},2,3,1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr] \\ &\qquad{} \times \biggl[\frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{2} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},1,3,\frac{1}{2} \biggl(1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr)\\ &\qquad{} - \frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{12} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},2,4,\frac{1}{2} \biggl(1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr) \\ &\qquad{}+\frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{3} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},2,4,1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr)- \frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{2} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},1,3,1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr], \\ &\vartheta _{4}^{*}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[ \vert 1-2t \vert (1-t) \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr] \\ &\qquad{}\times\biggl[ \vert 1-2r \vert (1-r) \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr]\, \mathrm{d}t\,\mathrm{d}r \\ &\quad= \biggl[\frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{2} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},1,3,\frac{1}{2} \biggl(1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr)\\ &\qquad{}-\frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{12} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},2,4,\frac{1}{2} \biggl(1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr) \\ &\qquad{}+\frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{3} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},2,4,1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr)- \frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{2} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},1,3,1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr] \\ & \qquad{}\times \biggl[\frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{2} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},1,3,\frac{1}{2} \biggl(1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr)\\ &\qquad{}- \frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{12} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},2,4,\frac{1}{2} \biggl(1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr) \\ &\qquad{}+\frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{3} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},2,4,1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr)- \frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{2} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},1,3,1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr], \end{aligned}

$$\vartheta _{5}(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}:\Omega )$$ and $$\vartheta _{6}(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}:\Omega )$$ are given in Theorem 2.

II. If we take $$h_{1}(t)=t^{s_{1}}$$ and $$h_{2}(r)=r^{s_{2}}$$ in Theorem 2, then

### Corollary 7

Under the assumptions of Theorem 2, if $$|\frac{\partial ^{2}f}{\partial r \,\partial t} |$$ is a Breckner type approximately two-dimensional harmonic $$(p_{1},s_{1})$$-$$(p_{2},s_{2})$$-convex function, then

\begin{aligned} & \bigl\vert \Xi \bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}},x,y: \Omega \bigr) \bigr\vert \\ &\quad\leq \frac{(b^{p_{1}}-a^{p_{1}})(d^{p_{2}}-c^{p_{2}})}{4p_{1}p_{2}a^{p_{1}}b^{p_{1}}c^{p_{2}}d^{p_{2}}} \biggl[\vartheta _{1}^{**} \bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,c) \biggr\vert \\ & \qquad{}+\vartheta _{2}^{**}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,c) \biggr\vert + \vartheta _{3}^{**}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,d) \biggr\vert \\ &\qquad{} +\vartheta _{4}^{**}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,d) \biggr\vert + \vartheta _{5}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr)\\ &\qquad{} + \vartheta _{6}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggr], \end{aligned}

where

\begin{aligned} &\vartheta _{1}^{**}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[ \vert 1-2t \vert t^{s_{1}} \biggl[\frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr]\\ &\qquad{}\times \biggl[ \vert 1-2r \vert r^{s_{2}} \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr]\,\mathrm{d}t\,\mathrm{d}r \\ &\quad= \biggl[ \frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{2^{s_{1}}(s_{1}+1)(s_{1}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},s_{1}+1,s_{1}+3,\frac{1}{2} \biggl(1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr) \\ &\qquad{}+\frac{ 2(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{(s_{1}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},s_{1}+2,s_{1}+3,1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr)\\ &\qquad{}- \frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{(s_{1}+1)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},s_{1}+1,s_{1}+2,1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr] \\ &\qquad{} \times \biggl[ \frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{2^{s_{2}}(s_{2}+1)(s_{2}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},s_{2}+1,s_{2}+3,\frac{1}{2} \biggl(1- \frac{d^{p_{2}}}{c^{p_{1}}} \biggr) \biggr) \\ &\qquad{}+\frac{ 2(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{(s_{2}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},s_{2}+2,s_{2}+3,1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr)\\ &\qquad{}- \frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{(1-s_{1})} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},s_{2}+1,s_{2}+2,1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr], \\ &\vartheta _{2}^{**}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[ \vert 1-2t \vert (1-t)^{s_{1}} \biggl[\frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr]\\ &\qquad{}\times \biggl[ \vert 1-2r \vert r^{s_{2}} \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr]\,\mathrm{d}t\,\mathrm{d}r \\ &\quad= \biggl[\frac{4(a^{p_{1}})^{1+\frac{1}{p_{1}}}}{(s_{1}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},s_{1}+2,s_{1}+3,1- \frac{a^{p_{1}}}{b^{p_{1}}} \biggr) \\ &\qquad{}- \frac{2(a^{p_{1}})^{1+\frac{1}{p_{1}}}}{(s_{1}+1)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},s_{1}+1,s_{1}+2,1-\frac{a^{p_{1}}}{b^{p_{1}}} \biggr) \\ &\qquad{} + \frac{(a^{p_{1}})^{1+\frac{1}{p_{1}}}}{2^{s_{1}}(s_{1}+1)(s_{1}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},s_{1}+1,s_{1}+3,\frac{1}{2} \biggl(1- \frac{a^{p_{1}}}{b^{p_{1}}} \biggr) \biggr) \\ &\qquad{} +\frac{ 2(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{(s_{1}+1)(s_{1}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},2,s_{1}+3,1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr)\\ &\qquad{} - \frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{(s_{1}+1)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},1,s_{1}+2,1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr] \\ &\qquad{} \times \biggl[ \frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{2^{s_{2}}(s_{2}+1)(s_{2}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},s_{2}+1,s_{2}+3,\frac{1}{2} \biggl(1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr) \\ &\qquad{} +\frac{ 2(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{(s_{2}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},s_{2}+2,s_{2}+3,1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \\ &\qquad{}- \frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{(s_{2}+1)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},s_{2}+1,s_{2}+2,1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr], \\ &\vartheta _{3}^{**}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[ \vert 1-2t \vert t^{s_{1}} \biggl[\frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr]\\ &\qquad{}\times \biggl[ \vert 1-2r \vert (1-r)^{s_{2}} \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr]\,\mathrm{d}t\,\mathrm{d}r \\ &\quad= \biggl[ \frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{2^{s_{1}}(s_{1}+1)(s_{1}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},s_{1}+1,s_{1}+3,\frac{1}{2} \biggl(1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr) \\ &\qquad{}+\frac{ 2(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{(s_{1}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},s_{1}+2,s_{1}+3,1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr)\\ &\qquad{}- \frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{(1-s_{1})} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},s_{1}+1,s_{1}+2,1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr] \\ &\qquad{}\times \biggl[\frac{4(c^{p_{2}})^{1+\frac{1}{p_{2}}}}{(s_{2}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},s_{2}+2,s_{2}+3,1- \frac{c^{p_{2}}}{d^{p_{2}}} \biggr) \\ &\qquad{}- \frac{2(c^{p_{2}})^{1+\frac{1}{p_{2}}}}{(s_{2}+1)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},s_{2}+1,s_{2}+2,1-\frac{c^{p_{2}}}{d^{p_{2}}} \biggr) \\ & \qquad{}+ \frac{(c^{p_{2}})^{1+\frac{1}{p_{2}}}}{2^{s_{2}}(s_{2}+1)(s_{2}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},s_{2}+1,s_{2}+3,\frac{1}{2} \biggl(1- \frac{c^{p_{2}}}{d^{p_{2}}} \biggr) \biggr) \\ &\qquad{} +\frac{ 2(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{(s_{2}+1)(s_{2}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},2,s_{2}+3,1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \\ &\qquad{}- \frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{(s_{2}+1)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},1,s_{2}+2,1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr], \\ &\vartheta _{4}^{**}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[ \vert 1-2t \vert (1-t)^{s_{1}} \biggl[\frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr]\\ &\qquad{}\times \biggl[ \vert 1-2r \vert (1-r)^{s_{2}} \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr]\,\mathrm{d}t\,\mathrm{d}r \\ &\quad= \biggl[\frac{4(a^{p_{1}})^{1+\frac{1}{p_{1}}}}{(s_{1}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},s_{1}+2,s_{1}+3,1- \frac{a^{p_{1}}}{b^{p_{1}}} \biggr)\\ &\qquad{} - \frac{2(a^{p_{1}})^{1+\frac{1}{p_{1}}}}{(s_{1}+1)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},s_{1}+1,s_{1}+2,1-\frac{a^{p_{1}}}{b^{p_{1}}} \biggr) \\ &\qquad{} + \frac{(a^{p_{1}})^{1+\frac{1}{p_{1}}}}{2^{s_{1}}(s_{1}+1)(s_{1}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},s_{1}+1,s_{1}+3,\frac{1}{2} \biggl(1- \frac{a^{p_{1}}}{b^{p_{1}}} \biggr) \biggr) \\ &\qquad{} +\frac{ 2(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{(s_{1}+1)(s_{1}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},2,s_{1}+3,1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \\ &\qquad{}- \frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{(s_{1}+1)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},1,s_{1}+2,1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr] \\ &\qquad{}\times \biggl[\frac{4(c^{p_{2}})^{1+\frac{1}{p_{2}}}}{(s_{2}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},s_{2}+2,s_{2}+3,1- \frac{c^{p_{2}}}{d^{p_{2}}} \biggr) \\ &\qquad{}- \frac{2(c^{p_{2}})^{1+\frac{1}{p_{2}}}}{(s_{2}+1)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},s_{2}+1,s_{2}+2,1-\frac{c^{p_{2}}}{d^{p_{2}}} \biggr) \\ & \qquad{}+ \frac{(c^{p_{2}})^{1+\frac{1}{p_{2}}}}{2^{s_{2}}(s_{2}+1)(s_{2}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},s_{2}+1,s_{2}+3,\frac{1}{2} \biggl(1- \frac{c^{p_{2}}}{d^{p_{2}}} \biggr) \biggr) \\ &\qquad{} +\frac{ 2(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{(s_{2}+1)(s_{2}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},2,s_{2}+3,1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \\ &\qquad{}- \frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{(s_{2}+1)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},1,s_{2}+2,1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr], \end{aligned}

$$\vartheta _{5}(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}:\Omega )$$ and $$\vartheta _{6}(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}:\Omega )$$ are given in Theorem 2.

III. If we take $$h_{1}(t)=t^{-s_{1}}$$ and $$h_{2}(r)=r^{-s_{2}}$$ in Theorem 2, then

### Corollary 8

Under the assumptions of Theorem 2, if $$|\frac{\partial ^{2}f}{\partial r \,\partial t} |$$ is a Godunova–Levin type approximately two-dimensional harmonic $$(p_{1},s_{1})$$-$$(p_{2},s_{2})$$-convex function, then

\begin{aligned} & \bigl\vert \Xi \bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}},x,y: \Omega \bigr) \bigr\vert \\ &\quad\leq \frac{(b^{p_{1}}-a^{p_{1}})(d^{p_{2}}-c^{p_{2}})}{4p_{1}p_{2}a^{p_{1}}b^{p_{1}}c^{p_{2}}d^{p_{2}}} \biggl[\vartheta _{1}^{\prime } \bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,c) \biggr\vert \\ & \qquad{}+\vartheta _{2}^{\prime }\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,c) \biggr\vert + \vartheta _{3}^{\prime }\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,d) \biggr\vert \\ &\qquad{} +\vartheta _{4}^{\prime }\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,d) \biggr\vert + \vartheta _{5}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr)\\ &\qquad{}+ \vartheta _{6}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggr], \end{aligned}

where

\begin{aligned} &\vartheta _{1}^{\prime }\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[ \vert 1-2t \vert t^{-s_{1}} \biggl[\frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr] \\ &\qquad{}\times\biggl[ \vert 1-2r \vert r^{-s_{2}} \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr]\,\mathrm{d}t\,\mathrm{d}r \\ &\quad= \biggl[ \frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{2^{-s_{1}}(-s_{1}+1)(-s_{1}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},-s_{1}+1,-s_{1}+3,\frac{1}{2} \biggl(1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr) \\ &\qquad{}+\frac{ 2(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{(-s_{1}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},-s_{1}+2,-s_{1}+3,1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \\ &\qquad{}-\frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{(-s_{1}+1)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},-s_{1}+1,-s_{1}+2,1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr] \\ &\qquad{} \times \biggl[ \frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{2^{-s_{2}}(-s_{2}+1)(-s_{2}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},-s_{2}+1,-s_{2}+3,\frac{1}{2} \biggl(1-\frac{d^{p_{2}}}{c^{p_{1}}} \biggr) \biggr) \\ &\qquad{}+\frac{ 2(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{(-s_{2}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},-s_{2}+2,-s_{2}+3,1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \\ &\qquad{}-\frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{(-s_{1}+1)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},-s_{2}+1,-s_{2}+2,1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr], \\ &\vartheta _{2}^{\prime }\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[ \vert 1-2t \vert (1-t)^{-s_{1}} \biggl[\frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr]\\ &\qquad{}\times \biggl[ \vert 1-2r \vert r^{-s_{2}} \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr]\,\mathrm{d}t\,\mathrm{d}r \\ &\quad= \biggl[\frac{4(a^{p_{1}})^{1+\frac{1}{p_{1}}}}{(-s_{1}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},-s_{1}+2,-s_{1}+3,1- \frac{a^{p_{1}}}{b^{p_{1}}} \biggr) \\ &\qquad{} - \frac{2(a^{p_{1}})^{1+\frac{1}{p_{1}}}}{(-s_{1}+1)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},-s_{1}+1,-s_{1}+2,1- \frac{a^{p_{1}}}{b^{p_{1}}} \biggr) \\ &\qquad{} + \frac{(a^{p_{1}})^{1+\frac{1}{p_{1}}}}{2^{-s_{1}}(-s_{1}+1)(-s_{1}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},-s_{1}+1,-s_{1}+3,\frac{1}{2} \biggl(1-\frac{a^{p_{1}}}{b^{p_{1}}} \biggr) \biggr) \\ &\qquad{} + \frac{ 2(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{(-s_{1}+1)(-s_{1}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},2,-s_{1}+3,1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \\ &\qquad{}-\frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{(-s_{1}+1)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},1,-s_{1}+2,1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr] \\ &\qquad{} \times \biggl[ \frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{2^{-s_{2}}(-s_{2}+1)(-s_{2}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},-s_{2}+1,-s_{2}+3,\frac{1}{2} \biggl(1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr) \\ & \qquad{}+\frac{ 2(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{(-s_{2}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},-s_{2}+2,-s_{2}+3,1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \\ &\qquad{}-\frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{(-s_{2}+1)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},-s_{2}+1,-s_{2}+2,1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr], \\ &\vartheta _{3}^{\prime }\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[ \vert 1-2t \vert t^{-s_{1}} \biggl[\frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr] \\ &\qquad{}\times\biggl[ \vert 1-2r \vert (1-r)^{-s_{2}} \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr]\,\mathrm{d}t\,\mathrm{d}r \\ &\quad= \biggl[ \frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{2^{-s_{1}}(-s_{1}+1)(-s_{1}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},-s_{1}+1,-s_{1}+3,\frac{1}{2} \biggl(1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr) \\ &\qquad{}+\frac{ 2(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{(-s_{1}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},-s_{1}+2,-s_{1}+3,1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \\ &\qquad{}-\frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{(-s_{1}+1)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},-s_{1}+1,-s_{1}+2,1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr] \\ &\qquad{}\times \biggl[\frac{4(c^{p_{2}})^{1+\frac{1}{p_{2}}}}{(-s_{2}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},-s_{2}+2,-s_{2}+3,1- \frac{c^{p_{2}}}{d^{p_{2}}} \biggr) \\ & \qquad{}- \frac{2(c^{p_{2}})^{1+\frac{1}{p_{2}}}}{(-s_{2}+1)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},-s_{2}+1,-s_{2}+2,1- \frac{c^{p_{2}}}{d^{p_{2}}} \biggr) \\ &\qquad{} + \frac{(c^{p_{2}})^{1+\frac{1}{p_{2}}}}{2^{-s_{2}}(-s_{2}+1)(-s_{2}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},-s_{2}+1,-s_{2}+3,\frac{1}{2} \biggl(1-\frac{c^{p_{2}}}{d^{p_{2}}} \biggr) \biggr) \\ &\qquad{} + \frac{ 2(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{(-s_{2}+1)(-s_{2}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},2,-s_{2}+3,1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \\ &\qquad{}-\frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{(-s_{2}+1)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},1,-s_{2}+2,1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr], \\ &\vartheta _{4}^{\prime }\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[ \vert 1-2t \vert (1-t)^{-s_{1}} \biggl[\frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr]\\ &\qquad{}\times \biggl[ \vert 1-2r \vert (1-r)^{-s_{2}} \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr]\,\mathrm{d}t\,\mathrm{d}r \\ &\quad= \biggl[\frac{4(a^{p_{1}})^{1+\frac{1}{p_{1}}}}{(-s_{1}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},-s_{1}+2,-s_{1}+3,1- \frac{a^{p_{1}}}{b^{p_{1}}} \biggr) \\ &\qquad{} - \frac{2(a^{p_{1}})^{1+\frac{1}{p_{1}}}}{(-s_{1}+1)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},-s_{1}+1,-s_{1}+2,1- \frac{a^{p_{1}}}{b^{p_{1}}} \biggr) \\ &\qquad{} + \frac{(a^{p_{1}})^{1+\frac{1}{p_{1}}}}{2^{-s_{1}}(-s_{1}+1)(-s_{1}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},-s_{1}+1,-s_{1}+3,\frac{1}{2} \biggl(1-\frac{a^{p_{1}}}{b^{p_{1}}} \biggr) \biggr) \\ &\qquad{} + \frac{ 2(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{(-s_{1}+1)(-s_{1}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},2,-s_{1}+3,1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \\ &\qquad{}-\frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{(-s_{1}+1)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},1,-s_{1}+2,1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr] \\ &\qquad{}\times \biggl[\frac{4(c^{p_{2}})^{1+\frac{1}{p_{2}}}}{(-s_{2}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},-s_{2}+2,-s_{2}+3,1- \frac{c^{p_{2}}}{d^{p_{2}}} \biggr) \\ &\qquad{} - \frac{2(c^{p_{2}})^{1+\frac{1}{p_{2}}}}{(-s_{2}+1)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},-s_{2}+1,-s_{2}+2,1- \frac{c^{p_{2}}}{d^{p_{2}}} \biggr) \\ &\qquad{} + \frac{(c^{p_{2}})^{1+\frac{1}{p_{2}}}}{2^{-s_{2}}(-s_{2}+1)(-s_{2}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},-s_{2}+1,-s_{2}+3,\frac{1}{2} \biggl(1-\frac{c^{p_{2}}}{d^{p_{2}}} \biggr) \biggr) \\ &\qquad{} + \frac{ 2(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{(-s_{2}+1)(-s_{2}+2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},2,-s_{2}+3,1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \\ &\qquad{}-\frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{(-s_{2}+1)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},1,-s_{2}+2,1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr], \end{aligned}

$$\vartheta _{5}(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}:\Omega )$$ and $$\vartheta _{6}(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}:\Omega )$$ are given in Theorem 2.

IV. If we take $$h(t)=1$$ and $$h(r)=1$$ in Theorem 2, then

### Corollary 9

Under the assumptions of Theorem 2, if $$|\frac{\partial ^{2}f}{\partial r \,\partial t} |$$ is an approximately two-dimensional harmonic $$(p_{1}, P)$$-$$(p_{2},P)$$-convex function, then

\begin{aligned} & \bigl\vert \Xi \bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}},x,y: \Omega \bigr) \bigr\vert \\ &\quad\leq \frac{(b^{p_{1}}-a^{p_{1}})(d^{p_{2}}-c^{p_{2}})}{4p_{1}p_{2}a^{p_{1}}b^{p_{1}}c^{p_{2}}d^{p_{2}}} \vartheta ^{\prime \prime }\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl[ \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,c) \biggr\vert \\ &\qquad{} + \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,c) \biggr\vert + \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,d) \biggr\vert + \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,d) \biggr\vert +\Delta (a,b)+ \Delta (c,d) \biggr], \end{aligned}

where

\begin{aligned} &\vartheta ^{\prime \prime }\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[ \vert 1-2t \vert \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr]\\ &\qquad{}\times \biggl[ \vert 1-2r \vert \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr]\,\mathrm{d}t\, \mathrm{d}r \\ &\quad= \biggl[ \bigl(b^{p_{1}}\bigr)^{1+\frac{1}{p_{1}}} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},2,3,1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr)- \bigl(b^{p_{1}}\bigr)^{1+ \frac{1}{p_{1}}} {}_{2}F_{1} \biggl(1+\frac{1}{p_{1}},1,2,1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \\ &\qquad{}+\frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{2} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},1,3,\frac{1}{2} \biggl(1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr) \biggr] \biggl[ \bigl(d^{p_{2}}\bigr)^{1+\frac{1}{p_{2}}} {}_{2}F_{1} \biggl(1+\frac{1}{p_{2}},2,3,1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \\ &\qquad{}-\bigl(d^{p_{2}}\bigr)^{1+\frac{1}{p_{2}}} {}_{2}F_{1} \biggl(1+\frac{1}{p_{2}},1,2,1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr)\\ &\qquad{}+ \frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{2} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},1,3, \frac{1}{2} \biggl(1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr) \biggr] \end{aligned}

V. If we take $$\Delta (a,b)=-\mu (t^{\sigma }(1-t)+t(1-t)^{\sigma } ) ( \Vert \frac{1}{b^{p_{1}}}-\frac{1}{a^{p_{1}}} \Vert )^{\sigma }$$ and $$\Delta (c,d)=-\mu (r^{\sigma }(1-r)+r(1-r)^{\sigma } ) ( \Vert \frac{1}{d^{p_{2}}}-\frac{1}{c^{p_{2}}} \Vert )^{\sigma }$$ for some $$\mu >0$$ in Theorem 2, then

### Corollary 10

Under the assumptions of Theorem 2, if $$|\frac{\partial ^{2}f}{\partial r \,\partial t} |$$ is a two-dimensional harmonically strong $$(p_{1},h_{1})$$-$$(p_{2},h_{2})$$-convex function with $$\mu >0$$ of higher order, then

\begin{aligned} & \bigl\vert \Xi \bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}},x,y: \Omega \bigr) \bigr\vert \\ &\quad\leq \frac{(b^{p_{1}}-a^{p_{1}})(d^{p_{2}}-c^{p_{2}})}{4p_{1}p_{2}a^{p_{1}}b^{p_{1}}c^{p_{2}}d^{p_{2}}} \biggl[\vartheta _{1}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,c) \biggr\vert \\ &\qquad{} +\vartheta _{2}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,c) \biggr\vert + \vartheta _{3}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,d) \biggr\vert \\ & \qquad{}+\vartheta _{4}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,d) \biggr\vert + \vartheta _{5}^{*}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr)\\ &\qquad{}+ \vartheta _{6}^{*}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggr], \end{aligned}

where $$\vartheta _{1}(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}:\Omega ), \vartheta _{2}(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}:\Omega ), \vartheta _{3}(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}:\Omega ), \vartheta _{4}(a^{p_{1}},b^{p_{1}}, c^{p_{2}},d^{p_{2}}:\Omega )$$ are given in Theorem 2and

\begin{aligned} &\vartheta _{5}^{*}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}; \Omega \bigr) \\ &\quad=-\mu \biggl( \biggl\Vert \frac{1}{b^{p_{1}}}-\frac{1}{a^{p_{1}}} \biggr\Vert \biggr)^{\sigma }\\ &\qquad{} \times \int _{0}^{1} \int _{0}^{1} \biggl( \vert 1-2t \vert \bigl(t^{\sigma }(1-t)+t(1-t)^{\sigma }\bigr) \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr) \\ &\qquad{} \times \biggl( \vert 1-2r \vert \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr)\,\mathrm{d}t\,\mathrm{d}r \\ &\quad=-\mu \biggl( \biggl\Vert \frac{1}{b^{p_{1}}}-\frac{1}{a^{p_{1}}} \biggr\Vert \biggr)^{\sigma } \biggl[ \frac{2(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{(\sigma +2)(\sigma +3)} {}_{2}F_{1} \biggl(1+\frac{1}{p_{1}},\sigma +2,\sigma +4,1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \\ &\qquad{} + \frac{2(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{(\sigma +3)(\sigma +2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},3,\sigma +4,1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \\ & \qquad{}- \frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{(\sigma +1)(\sigma +2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},\sigma +1,\sigma +3,1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \\ &\qquad{} - \frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{(\sigma +1)(\sigma +2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},2,\sigma +3,1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \\ &\qquad{} + \frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{2^{\sigma }(\sigma +1)(\sigma +2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},\sigma +1,\sigma +3,\frac{1}{2} \biggl(1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr) \\ & \qquad{}- \frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{2^{\sigma +1}(\sigma +2)(\sigma +3)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},\sigma +2,\sigma +4,\frac{1}{2} \biggl(1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr) \\ & \qquad{}+ \frac{4(a^{p_{1}})^{1+\frac{1}{p_{1}}}}{(\sigma +2)(\sigma +3)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},\sigma +2,\sigma +4,1- \frac{a^{p_{1}}}{b^{p_{1}}} \biggr) \\ &\qquad{} - \frac{2(a^{p_{1}})^{1+\frac{1}{p_{1}}}}{(\sigma +1)(\sigma +2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},\sigma +1,\sigma +3,1- \frac{a^{p_{1}}}{b^{p_{1}}} \biggr) \\ &\qquad{} + \frac{(a^{p_{1}})^{1+\frac{1}{p_{1}}}}{2^{\sigma }(\sigma +1)(\sigma +2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},\sigma +1,\sigma +3,\frac{1}{2} \biggl(1- \frac{a^{p_{1}}}{b^{p_{1}}} \biggr) \biggr) \\ & \qquad{}- \frac{(a^{p_{1}})^{1+\frac{1}{p_{1}}}}{2^{\sigma +1}(\sigma +2)(\sigma +3)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},\sigma +2,\sigma +4,\frac{1}{2} \biggl(1- \frac{a^{p_{1}}}{b^{p_{1}}} \biggr) \biggr) \biggr] \\ & \qquad{}\times \biggl[ \bigl(d^{p_{2}}\bigr)^{1+\frac{1}{p_{2}}} {}_{2}F_{1} \biggl(1+\frac{1}{p_{2}},2,3,1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr)- \bigl(d^{p_{2}}\bigr)^{1+ \frac{1}{p_{2}}} {}_{2}F_{1} \biggl(1+\frac{1}{p_{2}},1,2,1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \\ &\qquad{} +\frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{2} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},1,3,\frac{1}{2} \biggl(1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr) \biggr], \\ &\vartheta _{6}^{*}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}; \Omega \bigr) \\ &\quad=-\mu \biggl( \biggl\Vert \frac{1}{d^{p_{2}}}-\frac{1}{c^{p_{2}}} \biggr\Vert \biggr)^{\sigma }\times \int _{0}^{1} \int _{0}^{1} \biggl( \vert 1-2t \vert \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr) \\ &\qquad{}\times \biggl( \vert 1-2r \vert \bigl(r^{\sigma }(1-r)+r(1-r)^{\sigma } \bigr) \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr)\,\mathrm{d}t\, \mathrm{d}r \\ &\quad=-\mu \biggl( \biggl\Vert \frac{1}{d^{p_{2}}}-\frac{1}{c^{p_{2}}} \biggr\Vert \biggr)^{\sigma } \biggl[ \bigl(b^{p_{1}}\bigr)^{1+\frac{1}{p_{1}}} {}_{2}F_{1} \biggl(1+\frac{1}{p_{1}},2,3,1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \\ &\qquad{} - \bigl(b^{p_{1}}\bigr)^{1+\frac{1}{p_{1}}} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},1,2,1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) + \frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{2} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},1,3,\frac{1}{2} \biggl(1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr) \biggr] \\ &\qquad{} \times \biggl[ \frac{2(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{(\sigma +2)(\sigma +3)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},\sigma +2,\sigma +4,1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \\ &\qquad{} + \frac{2(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{(\sigma +3)(\sigma +2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},3,\sigma +4,1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \\ & \qquad{}- \frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{(\sigma +1)(\sigma +2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},\sigma +1,\sigma +3,1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \\ &\qquad{} - \frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{(\sigma +1)(\sigma +2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},2,\sigma +3,1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \\ & \qquad{}+ \frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{2^{\sigma }(\sigma +1)(\sigma +2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},\sigma +1,\sigma +3,\frac{1}{2} \biggl(1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr) \\ & \qquad{}- \frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{2^{\sigma +1}(\sigma +2)(\sigma +3)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},\sigma +2,\sigma +4,\frac{1}{2} \biggl(1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr) \\ &\qquad{} + \frac{4(c^{p_{2}})^{1+\frac{1}{p_{2}}}}{(\sigma +2)(\sigma +3)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},\sigma +2,\sigma +4,1- \frac{c^{p_{2}}}{d^{p_{2}}} \biggr) \\ &\qquad{} - \frac{2(c^{p_{2}})^{1+\frac{1}{p_{2}}}}{(\sigma +1)(\sigma +2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},\sigma +1,\sigma +3,1- \frac{c^{p_{2}}}{d^{p_{2}}} \biggr) \\ &\qquad{} + \frac{(c^{p_{2}})^{1+\frac{1}{p_{2}}}}{2^{\sigma }(\sigma +1)(\sigma +2)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},\sigma +1,\sigma +3,\frac{1}{2} \biggl(1- \frac{c^{p_{2}}}{d^{p_{2}}} \biggr) \biggr) \\ & \qquad{}- \frac{(c^{p_{2}})^{1+\frac{1}{p_{2}}}}{2^{\sigma +1}(\sigma +2)(\sigma +3)} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},\sigma +2,\sigma +4,\frac{1}{2} \biggl(1- \frac{c^{p_{2}}}{d^{p_{2}}} \biggr) \biggr) \biggr]. \end{aligned}

VI. If we take $$\sigma =2$$ in Corollary 10, then

### Corollary 11

Under the assumptions of Corollary 10, if $$|\frac{\partial ^{2}f}{\partial r \,\partial t} |$$ is a two-dimensional harmonically strong $$(p_{1},h_{1})$$-$$(p_{2},h_{2})$$-convex function with $$\mu >0$$, then

\begin{aligned} & \bigl\vert \Xi \bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}},x,y: \Omega \bigr) \bigr\vert \\ &\quad\leq \frac{(b^{p_{1}}-a^{p_{1}})(d^{p_{2}}-c^{p_{2}})}{4p_{1}p_{2}a^{p_{1}}b^{p_{1}}c^{p_{2}}d^{p_{2}}} \biggl[\vartheta _{1}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,c) \biggr\vert \\ &\qquad{} +\vartheta _{2}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,c) \biggr\vert + \vartheta _{3}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,d) \biggr\vert \\ &\qquad{} +\vartheta _{4}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,d) \biggr\vert + \vartheta _{5}^{**}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr)\\ &\qquad{}+ \vartheta _{6}^{**}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggr], \end{aligned}

where $$\vartheta _{1}(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}:\Omega ), \vartheta _{2}(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}:\Omega ), \vartheta _{3}(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}:\Omega ), \vartheta _{4}(a^{p_{1}}, b^{p_{1}},c^{p_{2}},d^{p_{2}}:\Omega )$$ are given in Theorem 2and

\begin{aligned} &\vartheta _{5}^{**}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}; \Omega \bigr) \\ &\quad=-\mu \biggl( \biggl\Vert \frac{1}{b^{p_{1}}}-\frac{1}{a^{p_{1}}} \biggr\Vert \biggr)^{2} \times \int _{0}^{1} \int _{0}^{1} ( \vert 1-2t \vert \biggl(t(1-t) \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr) \\ & \qquad{}\times \biggl( \vert 1-2r \vert \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr)\,\mathrm{d}t\,\mathrm{d}r \\ &\quad=-\mu \biggl( \biggl\Vert \frac{1}{b^{p_{1}}}-\frac{1}{a^{p_{1}}} \biggr\Vert \biggr)^{2} \biggl[\frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{4} {}_{2}F_{1} \biggl(1+\frac{1}{p_{1}},2,3,\frac{1}{2} \biggl(1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr) \\ &\qquad{}-\frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{4} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},3,4,\frac{1}{2} \biggl(1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr) \\ &\qquad{} +\frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{16} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},4,5,\frac{1}{2} \biggl(1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr)\\ &\qquad{}+\bigl(b^{p_{1}}\bigr)^{1+\frac{1}{p_{1}}} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},3,4,\biggl(1-\frac{b^{p_{1}}}{a^{p_{1}}}\biggr) \biggr) \\ &\qquad{} -\frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{2} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},4,5,\biggl(1-\frac{b^{p_{1}}}{a^{p_{1}}}\biggr) \biggr)\\ &\qquad{}- \frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{2} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},2,3,\biggl(1-\frac{b^{p_{1}}}{a^{p_{1}}}\biggr) \biggr) \biggr] \\ &\qquad{} \times \biggl[ \bigl(d^{p_{2}}\bigr)^{1+\frac{1}{p_{2}}} {}_{2}F_{1} \biggl(1+\frac{1}{p_{2}},2,3,1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr)- \bigl(d^{p_{2}}\bigr)^{1+ \frac{1}{p_{2}}} {}_{2}F_{1} \biggl(1+\frac{1}{p_{2}},1,2,1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \\ & \qquad{}+\frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{2} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},1,3,\frac{1}{2} \biggl(1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr) \biggr], \\ &\vartheta _{6}^{**}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}; \Omega \bigr) \\ &\quad=-\mu \biggl( \biggl\Vert \frac{1}{d^{p_{2}}}-\frac{1}{c^{p_{2}}} \biggr\Vert \biggr)^{2} \times \int _{0}^{1} \int _{0}^{1} \biggl( \vert 1-2t \vert \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr) \\ &\qquad{} \times \biggl( \vert 1-2r \vert r(1-r) \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr)\,\mathrm{d}t\,\mathrm{d}r \\ &\qquad{} -\mu \biggl( \biggl\Vert \frac{1}{d^{p_{2}}}-\frac{1}{c^{p_{2}}} \biggr\Vert \biggr)^{2}\times \biggl[ \bigl(b^{p_{1}} \bigr)^{1+\frac{1}{p_{1}}} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},2,3,1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \\ & \qquad{}- \bigl(d^{p_{1}}\bigr)^{1+\frac{1}{p_{1}}} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},1,2,1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \\ &\qquad{} +\frac{(b^{p_{1}})^{1+\frac{1}{p_{1}}}}{2} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{1}},1,3,\frac{1}{2} \biggl(1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr) \biggr] \\ &\qquad{} \times \biggl[\frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{4} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},2,3,\frac{1}{2} \biggl(1- \frac{d^{p_{2}}}{a^{p_{2}}} \biggr) \biggr) \\ &\qquad{}-\frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{4} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},3,4,\frac{1}{2} \biggl(1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr) \\ &\qquad{} +\frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{16} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},4,5,\frac{1}{2} \biggl(1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr)\\ &\qquad{}+\bigl(d^{p_{2}}\bigr)^{1+\frac{1}{p_{2}}} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},3,4,\biggl(1-\frac{d^{p_{2}}}{c^{p_{2}}}\biggr) \biggr) \\ & \qquad{}-\frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{2} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},4,5,\biggl(1-\frac{d^{p_{2}}}{c^{p_{2}}}\biggr) \biggr)\\ &\qquad{}- \frac{(d^{p_{2}})^{1+\frac{1}{p_{2}}}}{2} {}_{2}F_{1} \biggl(1+ \frac{1}{p_{2}},2,3,\biggl(1-\frac{d^{p_{2}}}{c^{p_{2}}}\biggr) \biggr) \biggr]. \end{aligned}

### Theorem 3

Let $$f:\Omega \rightarrow \mathbb{R}$$ be a partial differentiable function on $$\Omega = [a,b]\times [c,d]\subset (0,\infty )\times (0,\infty )$$ with $$a< b$$ and $$c< d$$ and $$\frac{\partial ^{2}f}{\partial t \partial r}\in L_{1}(\Omega )$$. If $$|\frac{\partial ^{2}f}{\partial r \,\partial t} |^{q}$$ is an approximately two-dimensional harmonic $$(p_{1},h_{1})$$-$$(p_{2},h_{2})$$-convex function, where $$\frac{1}{p}+\frac{1}{q}=1$$ and $$q>1$$, we have

\begin{aligned} & \bigl\vert \Xi \bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}},x,y: \Omega \bigr) \bigr\vert \\ &\quad\leq \frac{(b^{p_{1}}-a^{p_{1}})(d^{p_{2}}-c^{p_{2}})}{4p_{1}p_{2}a^{p_{1}}b^{p_{1}}c^{p_{2}}d^{p_{2}}(p+1)^{\frac{2}{p}}} \biggl[\varphi _{1}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,c) \biggr\vert ^{q} \\ & \qquad{}+\varphi _{2}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,c) \biggr\vert ^{q} + \varphi _{3}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,d) \biggr\vert ^{q} \\ &\qquad{} +\varphi _{4}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,d) \biggr\vert ^{q} + \varphi _{5}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr)\\ &\qquad{}+ \varphi _{6}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggr]^{\frac{1}{q}}, \end{aligned}

where

\begin{aligned} &\varphi _{1}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}; \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[h_{1}(t) \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{q (1+ \frac{1}{p_{1}} )} \biggr] \\ &\qquad{}\times\biggl[h_{2}(r) \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{q (1+ \frac{1}{p_{2}} )} \biggr]\,\mathrm{d}t\, \mathrm{d}r, \\ &\varphi _{2}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}; \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[h_{1}(1-t) \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{q (1+ \frac{1}{p_{1}} )} \biggr] \\ &\qquad{}\times\biggl[h_{2}(r) \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{q (1+ \frac{1}{p_{2}} )} \biggr]\,\mathrm{d}t\, \mathrm{d}r, \\ &\varphi _{3}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}; \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[h_{1}(t) \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{q (1+ \frac{1}{p_{1}} )} \biggr]\\ &\qquad{}\times \biggl[h_{2}(1-r) \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{q (1+ \frac{1}{p_{2}} )} \biggr]\,\mathrm{d}t\, \mathrm{d}r, \\ &\varphi _{4}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}; \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[h_{1}(1-t) \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{q (1+ \frac{1}{p_{1}} )} \biggr] \\ &\qquad{}\times\biggl[h_{2}(1-r) \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{q (1+ \frac{1}{p_{2}} )} \biggr]\,\mathrm{d}t\, \mathrm{d}r, \\ &\varphi _{5}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}; \Omega \bigr) \\ &\quad=\Delta (a,b) \int _{0}^{1} \int _{0}^{1} \biggl[ \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{q (1+ \frac{1}{p_{1}} )} \biggr] \\ &\qquad{}\times\biggl[ \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{q (1+ \frac{1}{p_{2}} )} \biggr]\,\mathrm{d}t\,\mathrm{d}r \\ &\quad=\Delta (a,b) \biggl( \biggl[\bigl(b^{p_{1}}\bigr)^{q (1+\frac{1}{p_{1}} )} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{1}} \biggr),1,2,1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr] \\ &\qquad{}\times \biggl[\bigl(d^{p_{2}}\bigr)^{q (1+\frac{1}{p_{2}} )} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{2}} \biggr),1,2,1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr] \biggr), \end{aligned}

and

\begin{aligned} &\varphi _{6}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}; \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[ \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{q (1+ \frac{1}{p_{1}} )} \biggr] \biggl[ \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{q (1+ \frac{1}{p_{2}} )} \biggr]\,\mathrm{d}t\,\mathrm{d}r \\ &\quad=\Delta (c,d) \biggl( \biggl[\bigl(b^{p_{1}}\bigr)^{q (1+\frac{1}{p_{1}} )} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{1}} \biggr),1,2,1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr] \\ &\qquad{}\times \biggl[\bigl(d^{p_{2}}\bigr)^{q (1+\frac{1}{p_{2}} )} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{2}} \biggr),1,2,1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr] \biggr). \end{aligned}

### Proof

Using Lemma 1, well-known Hölder’s inequality, and the fact that $$|\frac{\partial ^{2}f}{\partial r \,\partial t} |^{q}$$ is an approximately two-dimensional harmonic $$(p_{1},h_{1})$$-$$(p_{2},h_{2})$$-convex function, we have

\begin{aligned} & \bigl\vert \Xi \bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}},x,y: \Omega \bigr) \bigr\vert \\ &\quad= \biggl\vert \frac{(b^{p_{1}}-a^{p_{1}})(d^{p_{2}}-c^{p_{2}})}{4p_{1}p_{2}a^{p_{1}}b^{p_{1}}c^{p_{2}}d^{p_{2}}} \int _{0}^{1} \int _{0}^{1} \biggl((1-2t) \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{1+ \frac{1}{p_{1}}} \biggr) \\ &\qquad{}\times\biggl((1-2r) \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{1+ \frac{1}{p_{2}}} \biggr) \\ &\qquad{} \times \frac{\partial ^{2}f}{\partial r \,\partial t} \biggl( \biggl[\frac{a^{p_{1}}b^{p_{1}}}{tb^{p_{1}}+(1-t)a^{p_{1}}} \biggr]^{ \frac{1}{p_{1}}}, \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{rd^{p_{2}}+(1-r)c^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}} \biggr)\, \mathrm{d}r\,\mathrm{d}t \biggr\vert \\ &\quad\leq \frac{(b^{p_{1}}-a^{p_{1}})(d^{p_{2}}-c^{p_{2}})}{4p_{1}p_{2}a^{p_{1}}b^{p_{1}}c^{p_{2}}d^{p_{2}}} \int _{0}^{1} \int _{0}^{1} \bigl( \bigl\vert (1-2t) (1-2r) \bigr\vert ^{p} \,\mathrm{d}r\,\mathrm{d}t \bigr)^{\frac{1}{p}} \\ &\qquad{} \times \biggl( \int _{0}^{1} \int _{0}^{1} \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{q (1+ \frac{1}{p_{1}} )} \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{q (1+ \frac{1}{p_{2}} )} \\ &\qquad{} \times \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t} \biggl( \biggl[\frac{a^{p_{1}}b^{p_{1}}}{tb^{p_{1}}+(1-t)a^{p_{1}}} \biggr]^{ \frac{1}{p_{1}}}, \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{rd^{p_{2}}+(1-r)c^{p_{2}}} \biggr]^{ \frac{1}{p_{2}}} \biggr) \biggr\vert ^{q}\,\mathrm{d}r\,\mathrm{d}t \biggr)^{\frac{1}{q}} \\ &\quad\leq \frac{(b^{p_{1}}-a^{p_{1}})(d^{p_{2}}-c^{p_{2}})}{4p_{1}p_{2}a^{p_{1}}b^{p_{1}}c^{p_{2}}d^{p_{2}}(p+1)^{\frac{2}{p}}} \\ &\qquad{}\times\biggl( \int _{0}^{1} \int _{0}^{1} \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{q (1+ \frac{1}{p_{1}} )} \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{q (1+ \frac{1}{p_{2}} )} \\ & \qquad{}\times \biggl[h_{1}(t)h_{2}(r) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,c) \biggr\vert ^{q}+h_{1}(1-t)h_{2}(r) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,c) \biggr\vert ^{q} \\ &\qquad{}+h_{1}(t)h_{2}(1-r) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,d) \biggr\vert ^{q} \\ &\qquad{} +h_{1}(1-t)h_{2}(1-r) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,d) \biggr\vert ^{q} +\Delta (a,b)+ \Delta (c,d) \biggr]\,\mathrm{d}r\,\mathrm{d}t \biggr)^{\frac{1}{q}}. \end{aligned}

This completes the proof. □

### Corollary 12

Under the assumptions of Theorem 2, if $$|\frac{\partial ^{2}f}{\partial r \,\partial t} |\le M$$ is a bounded function for $$M>0$$ on Ω, then

\begin{aligned} & \bigl\vert \Xi \bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}},x,y: \Omega \bigr) \bigr\vert \\ &\quad\leq \frac{M(b^{p_{1}}-a^{p_{1}})(d^{p_{2}}-c^{p_{2}})}{4p_{1}p_{2}a^{p_{1}}b^{p_{1}}c^{p_{2}}d^{p_{2}}(p+1)^{\frac{2}{p}}} \biggl[\varphi _{1}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \\ &\qquad{} +\varphi _{2}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) + \varphi _{3}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \\ &\qquad{} +\varphi _{4}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) + \frac{1}{M^{q}}\varphi _{5}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr)\\ &\qquad{}+\frac{1}{M^{q}}\varphi _{6}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggr]^{\frac{1}{q}}, \end{aligned}

where $$\varphi _{1}(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}:\Omega )$$ to $$\varphi _{6}(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}:\Omega )$$ are given in Theorem 3.

We now discuss some special cases of Theorem 3.

I. If we take $$h_{1}(t)=t$$ and $$h_{2}(r)=r$$ in Theorem 3, then

### Corollary 13

Under the assumptions of Theorem 3, if $$|\frac{\partial ^{2}f}{\partial r \,\partial t} |^{q}$$ is an approximately two-dimensional harmonic $$(p_{1},p_{2})$$-convex function, where $$\frac{1}{p}+\frac{1}{q}=1$$ and $$q>1$$, then

\begin{aligned} & \bigl\vert \Xi \bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}},x,y: \Omega \bigr) \bigr\vert \\ &\leq \frac{(b^{p_{1}}-a^{p_{1}})(d^{p_{2}}-c^{p_{2}})}{4p_{1}p_{2}a^{p_{1}}b^{p_{1}}c^{p_{2}}d^{p_{2}}(p+1)^{\frac{2}{p}}} \biggl[\varphi _{1}^{*} \bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,c) \biggr\vert ^{q} \\ & \qquad{}+\varphi _{2}^{*}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,c) \biggr\vert ^{q} +\varphi _{3}^{*}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,d) \biggr\vert ^{q} \\ &\qquad{} +\varphi _{4}^{*}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,d) \biggr\vert ^{q} +\varphi _{5}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr)\\ &\qquad{}+ \varphi _{6}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggr]^{\frac{1}{q}}, \end{aligned}

where

\begin{aligned} &\varphi _{1}^{*}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}; \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[t \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{q (1+ \frac{1}{p_{1}} )} \biggr] \biggl[r \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{q (1+ \frac{1}{p_{2}} )} \biggr]\,\mathrm{d}t\,\mathrm{d}r \\ &\quad= \biggl[ \frac{(b^{p_{1}})^{q (1+\frac{1}{p_{1}} )}}{2} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{1}} \biggr),2,3,1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr]\\ &\qquad{}\times \biggl[ \frac{(d^{p_{2}})^{q (1+\frac{1}{p_{2}} )}}{2} {}_{2}F_{1} \biggl(q \biggl(1+ \frac{1}{p_{2}} \biggr),2,3,1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr], \\ &\varphi _{2}^{*}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}; \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[(1-t) \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{q (1+ \frac{1}{p_{1}} )} \biggr]\\ &\qquad{}\times \biggl[r \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{q (1+ \frac{1}{p_{2}} )} \biggr]\,\mathrm{d}t\,\mathrm{d}r \\ &\quad= \biggl[ \frac{(b^{p_{1}})^{q (1+\frac{1}{p_{1}} )}}{2} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{1}} \biggr),1,3,1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr]\\ &\qquad{}\times \biggl[ \frac{(d^{p_{2}})^{q (1+\frac{1}{p_{2}} )}}{2} {}_{2}F_{1} \biggl(q \biggl(1+ \frac{1}{p_{2}} \biggr),2,3,1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr], \\ &\varphi _{3}^{*}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}; \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[t \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{q (1+ \frac{1}{p_{1}} )} \biggr] \\ &\qquad{}\times\biggl[(1-r) \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{q (1+ \frac{1}{p_{2}} )} \biggr]\,\mathrm{d}t\,\mathrm{d}r \\ &\quad= \biggl[ \frac{(b^{p_{1}})^{q (1+\frac{1}{p_{1}} )}}{2} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{1}} \biggr),2,3,1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr]\\ &\qquad{}\times \biggl[ \frac{(d^{p_{2}})^{q (1+\frac{1}{p_{2}} )}}{2} {}_{2}F_{1} \biggl(q \biggl(1+ \frac{1}{p_{2}} \biggr),1,3,1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr], \\ &\varphi _{4}^{*}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}; \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[(1-t) \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{q (1+ \frac{1}{p_{1}} )} \biggr]\\ &\qquad{}\times \biggl[(1-r) \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{q (1+ \frac{1}{p_{2}} )} \biggr]\,\mathrm{d}t\,\mathrm{d}r \\ &\quad= \biggl[ \frac{(b^{p_{1}})^{q (1+\frac{1}{p_{1}} )}}{2} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{1}} \biggr),1,3,1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr]\\ &\qquad{}\times \biggl[ \frac{(d^{p_{2}})^{q (1+\frac{1}{p_{2}} )}}{2} {}_{2}F_{1} \biggl(q \biggl(1+ \frac{1}{p_{2}} \biggr),1,3,1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr], \end{aligned}

$$\varphi _{5}(a,b,c,d;\Omega )$$ and $$\varphi _{6}(a,b,c,d;\Omega )$$ are given in Theorem 3.

II. If we take $$h_{1}(t)=t^{s_{1}}$$ and $$h_{2}(r)=r^{s_{2}}$$ in Theorem 3, then

### Corollary 14

Under the assumptions of Theorem 3, if $$|\frac{\partial ^{2}f}{\partial r \,\partial t} |^{q}$$ is a Breckner type approximately two-dimensional harmonic $$(p_{1},s_{1})$$-$$(p_{2},s_{2})$$-convex function, where $$\frac{1}{p}+\frac{1}{q}=1$$ and $$q>1$$, then

\begin{aligned} & \bigl\vert \Xi \bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}},x,y: \Omega \bigr) \bigr\vert \\ &\quad\leq \frac{(b^{p_{1}}-a^{p_{1}})(d^{p_{2}}-c^{p_{2}})}{4p_{1}p_{2}a^{p_{1}}b^{p_{1}}c^{p_{2}}d^{p_{2}}(p+1)^{\frac{2}{p}}} \biggl[\varphi _{1}^{**} \bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,c) \biggr\vert ^{q} \\ &\qquad{} +\varphi _{2}^{**}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,c) \biggr\vert ^{q} +\varphi _{3}^{**}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,d) \biggr\vert ^{q} \\ &\qquad{} +\varphi _{4}^{**}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,d) \biggr\vert ^{q} +\varphi _{5}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr)\\ &\qquad{}+ \varphi _{6}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggr]^{\frac{1}{q}}, \end{aligned}

where

\begin{aligned} &\varphi _{1}^{**}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}; \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[t^{s_{1}} \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{q (1+ \frac{1}{p_{1}} )} \biggr] \biggl[r^{s_{2}} \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{q (1+ \frac{1}{p_{2}} )} \biggr]\,\mathrm{d}t\,\mathrm{d}r \\ &\quad= \biggl[ \frac{(b^{p_{1}})^{q (1+\frac{1}{p_{1}} )}}{s_{1}+1} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{1}} \biggr),s_{1}+1,s_{1}+2,1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr] \\ & \qquad{}\times \biggl[ \frac{(d^{p_{2}})^{q (1+\frac{1}{p_{2}} )}}{s_{2}+1} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{2}} \biggr),s_{2}+1,s_{2}+2,1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr], \\ &\varphi _{2}^{**}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}; \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[(1-t)^{s_{1}} \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{q (1+ \frac{1}{p_{1}} )} \biggr] \\ &\qquad{}\times\biggl[r^{s_{2}} \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{q (1+ \frac{1}{p_{2}} )} \biggr]\,\mathrm{d}t\,\mathrm{d}r \\ &\quad= \biggl[ \frac{(b^{p_{1}})^{q (1+\frac{1}{p_{1}} )}}{s_{1}+1} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{1}} \biggr),1,s_{1}+2,1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr] \\ &\qquad{} \times \biggl[ \frac{(d^{p_{2}})^{q (1+\frac{1}{p_{2}} )}}{s_{2}+1} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{2}} \biggr),s_{2}+1,s_{2}+2,1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr], \\ &\varphi _{3}^{**}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}; \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[t^{s_{1}} \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{q (1+ \frac{1}{p_{1}} )} \biggr] \\ &\qquad{}\times\biggl[(1-r)^{s_{2}} \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{q (1+ \frac{1}{p_{2}} )} \biggr]\,\mathrm{d}t\, \mathrm{d}r \\ &\quad= \biggl[ \frac{(b^{p_{1}})^{q (1+\frac{1}{p_{1}} )}}{s_{1}+1} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{1}} \biggr),s_{1}+1,s_{1}+2,1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr] \\ &\qquad{} \times \biggl[ \frac{(d^{p_{2}})^{q (1+\frac{1}{p_{2}} )}}{s_{2}+1} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{2}} \biggr),1,s_{2}+2,1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr], \\ &\varphi _{4}^{**}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}; \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[(1-t)^{s_{1}} \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{q (1+ \frac{1}{p_{1}} )} \biggr]\\ &\qquad{}\times \biggl[(1-r)^{s_{2}} \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{q (1+ \frac{1}{p_{2}} )} \biggr]\,\mathrm{d}t\, \mathrm{d}r \\ &\quad= \biggl[ \frac{(b^{p_{1}})^{q (1+\frac{1}{p_{1}} )}}{s_{1}+1} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{1}} \biggr),1,s_{1}+2,1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr] \\ &\qquad{} \times \biggl[ \frac{(d^{p_{2}})^{q (1+\frac{1}{p_{2}} )}}{s_{2}+1} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{2}} \biggr),1,s_{2}+2,1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr], \end{aligned}

$$\varphi _{5}(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}};\Omega )$$ and $$\varphi _{6}(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}};\Omega )$$ are given in Theorem 3.

III. If we take $$h_{1}(t)=t^{-s_{1}}$$ and $$h_{2}(r)=r^{-s_{2}}$$ in Theorem 3, then

### Corollary 15

Under the assumptions of Theorem 3, if $$|\frac{\partial ^{2}f}{\partial r \,\partial t} |^{q}$$ is a Godunova–Levin type approximately two-dimensional harmonic $$(p_{1},s_{1})$$-$$(p_{2},s_{2})$$-convex function, where $$\frac{1}{p}+\frac{1}{q}=1$$ and $$q>1$$, we have

\begin{aligned} & \bigl\vert \Xi \bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}},x,y: \Omega \bigr) \bigr\vert \\ &\quad\leq \frac{(b^{p_{1}}-a^{p_{1}})(d^{p_{2}}-c^{p_{2}})}{4p_{1}p_{2}a^{p_{1}}b^{p_{1}}c^{p_{2}}d^{p_{2}}(p+1)^{\frac{2}{p}}} \biggl[\varphi _{1}^{***} \bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,c) \biggr\vert ^{q} \\ &\qquad{} +\varphi _{2}^{***}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,c) \biggr\vert ^{q} +\varphi _{3}^{***}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,d) \biggr\vert ^{q} \\ &\qquad{} +\varphi _{4}^{***}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,d) \biggr\vert ^{q} +\varphi _{5}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr)\\ &\qquad{}+ \varphi _{6}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggr]^{\frac{1}{q}}, \end{aligned}

where

\begin{aligned} &\varphi _{1}^{***}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}; \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[t^{-s_{1}} \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{q (1+ \frac{1}{p_{1}} )} \biggr] \biggl[r^{-s_{2}} \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{q (1+ \frac{1}{p_{2}} )} \biggr]\,\mathrm{d}t\,\mathrm{d}r \\ &\quad= \biggl[ \frac{(b^{p_{1}})^{q (1+\frac{1}{p_{1}} )}}{1-s_{1}} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{1}} \biggr),1-s_{1},2-s_{1},1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr] \\ &\qquad{} \times \biggl[ \frac{(d^{p_{2}})^{q (1+\frac{1}{p_{2}} )}}{1-s_{2}} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{2}} \biggr),1-s_{2},2-s_{2},1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr], \\ &\varphi _{2}^{***}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}; \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[(1-t)^{-s_{1}} \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{q (1+ \frac{1}{p_{1}} )} \biggr]\\ &\qquad{}\times \biggl[r^{-s_{2}} \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{q (1+ \frac{1}{p_{2}} )} \biggr]\,\mathrm{d}t\,\mathrm{d}r \\ &\quad= \biggl[ \frac{(b^{p_{1}})^{q (1+\frac{1}{p_{1}} )}}{1-s_{1}} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{1}} \biggr),1,2-s_{1},1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr] \\ &\qquad{} \times \biggl[ \frac{(d^{p_{2}})^{q (1+\frac{1}{p_{2}} )}}{1-s_{2}} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{2}} \biggr),1-s_{2},2-s_{2},1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr], \\ &\varphi _{3}^{***}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}; \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[t^{-s_{1}} \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{q (1+ \frac{1}{p_{1}} )} \biggr] \\ &\qquad{}\times\biggl[(1-r)^{-s_{2}} \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{q (1+ \frac{1}{p_{2}} )} \biggr]\,\mathrm{d}t\, \mathrm{d}r \\ &\quad= \biggl[ \frac{(b^{p_{1}})^{q (1+\frac{1}{p_{1}} )}}{1-s_{1}} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{1}} \biggr),1-s_{1},2-s_{1},1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr] \\ & \qquad{}\times \biggl[ \frac{(d^{p_{2}})^{q (1+\frac{1}{p_{2}} )}}{1-s_{2}} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{2}} \biggr),1,2-s_{2},1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr], \\ &\varphi _{4}^{***}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}; \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[(1-t)^{-s_{1}} \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{q (1+ \frac{1}{p_{1}} )} \biggr] \\ &\qquad{}\times\biggl[(1-r)^{-s_{2}} \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{q (1+ \frac{1}{p_{2}} )} \biggr]\,\mathrm{d}t\, \mathrm{d}r \\ &\quad= \biggl[ \frac{(b^{p_{1}})^{q (1+\frac{1}{p_{1}} )}}{1-s_{1}} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{1}} \biggr),1,2-s_{1},1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr] \\ &\qquad{} \times \biggl[ \frac{(d^{p_{2}})^{q (1+\frac{1}{p_{2}} )}}{1-s_{2}} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{2}} \biggr),1,2-s_{2},1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr], \end{aligned}

$$\varphi _{5}(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}};\Omega )$$ and $$\varphi _{6}(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}};\Omega )$$ are given in Theorem 3.

IV. If we take $$h_{1}(t)=1$$ and $$h_{2}(r)=1$$ in Theorem 3, then

### Corollary 16

Under the assumptions of Theorem 3, if $$|\frac{\partial ^{2}f}{\partial r \,\partial t} |^{q}$$ is an approximately two-dimensional harmonic $$(p_{1},P)$$-$$(p_{2},P)$$-convex function, where $$\frac{1}{p}+\frac{1}{q}=1$$ and $$q>1$$, then

\begin{aligned} & \bigl\vert \Xi \bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}},x,y: \Omega \bigr) \bigr\vert \\ &\quad\leq \frac{(b^{p_{1}}-a^{p_{1}})(d^{p_{2}}-c^{p_{2}})}{4p_{1}p_{2}a^{p_{1}}b^{p_{1}}c^{p_{2}}d^{p_{2}}(p+1)^{\frac{2}{p}}}\bigl[ \varphi \bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr)\bigr]^{ \frac{1}{q}} \biggl[ \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,c) \biggr\vert ^{q} \\ &\qquad + \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,c) \biggr\vert ^{q}+ \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,d) \biggr\vert ^{q}+ \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,d) \biggr\vert ^{q}+ \Delta (a,b)+\Delta (c,d) \biggr]^{\frac{1}{q}}, \end{aligned}

where

\begin{aligned} &\varphi \bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}; \Omega \bigr) \\ &\quad= \int _{0}^{1} \int _{0}^{1} \biggl[ \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{q (1+ \frac{1}{p_{1}} )} \biggr] \biggl[ \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{q (1+ \frac{1}{p_{2}} )} \biggr]\,\mathrm{d}t\,\mathrm{d}r \\ &\quad= \biggl( \biggl[\bigl(b^{p_{1}}\bigr)^{q (1+\frac{1}{p_{1}} )} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{1}} \biggr),1,2,1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr] \\ &\qquad{}\times \biggl[\bigl(d^{p_{2}}\bigr)^{q (1+\frac{1}{p_{2}} )} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{2}} \biggr),1,2,1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr] \biggr). \end{aligned}

V. If we take $$\Delta (a,b)=-\mu (t^{\sigma }(1-t)+t(1-t)^{\sigma } ) ( \Vert \frac{1}{b^{p_{1}}}-\frac{1}{a^{p_{1}}} \Vert )^{\sigma }$$ and $$\Delta (c,d)=-\mu (r^{\sigma }(1-r)+r(1-r)^{\sigma } ) ( \Vert \frac{1}{d^{p_{2}}}-\frac{1}{c^{p_{2}}} \Vert )^{\sigma }$$ for some $$\mu >0$$ in Theorem 3, then

### Corollary 17

Under the assumptions of Theorem 3, if $$|\frac{\partial ^{2}f}{\partial r \,\partial t} |^{q}$$ is a two-dimensional harmonically strong $$(p_{1},h_{1})$$-$$(p_{2},h_{2})$$-convex function of higher order, where $$\frac{1}{p}+\frac{1}{q}=1$$ and $$q>1$$, then

\begin{aligned} & \bigl\vert \Xi \bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}},x,y: \Omega \bigr) \bigr\vert \\ &\quad\leq \frac{(b^{p_{1}}-a^{p_{1}})(d^{p_{2}}-c^{p_{2}})}{4p_{1}p_{2}a^{p_{1}}b^{p_{1}}c^{p_{2}}d^{p_{2}}(p+1)^{\frac{2}{p}}} \biggl[\varphi _{1}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,c) \biggr\vert ^{q} \\ &\qquad{} +\varphi _{2}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,c) \biggr\vert ^{q} + \varphi _{3}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,d) \biggr\vert ^{q} \\ &\qquad{} +\varphi _{4}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,d) \biggr\vert ^{q} + \varphi _{5}^{*}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr)\\ &\qquad{}+ \varphi _{6}^{*}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggr]^{\frac{1}{q}}, \end{aligned}

where $$\varphi _{1}(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}:\Omega ), \varphi _{2}(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}:\Omega ), \varphi _{3}(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}:\Omega ), \varphi _{4}(a^{p_{1}},b^{p_{1}}, c^{p_{2}},d^{p_{2}}:\Omega )$$ are given in Theorem 3, and

\begin{aligned} &\varphi _{5}^{*}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}; \Omega \bigr) \\ &\quad=-\mu \biggl( \biggl\Vert \frac{1}{b^{p_{1}}}-\frac{1}{a^{p_{1}}} \biggr\Vert \biggr)^{\sigma } \biggl( \int _{0}^{1} \int _{0}^{1} \biggl[ \bigl(t^{\sigma }(1-t)+t(1-t)^{\sigma } \bigr) \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{q (1+ \frac{1}{p_{1}} )} \biggr] \\ &\qquad{} \times \biggl[ \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{q (1+ \frac{1}{p_{2}} )} \biggr]\, \mathrm{d}t\,\mathrm{d}r\biggr) \\ &\quad=-\mu \biggl( \biggl\Vert \frac{1}{b^{p_{1}}}-\frac{1}{a^{p_{1}}} \biggr\Vert \biggr)^{\sigma } \biggl( \biggl[ \frac{(b^{p_{1}})^{q (1+\frac{1}{p_{1}} )}}{(\sigma +1)(\sigma +2)} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{1}} \biggr), \sigma +1,\sigma +3,1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \\ &\qquad{} + \frac{(b^{p_{1}})^{q (1+\frac{1}{p_{1}} )}}{(\sigma +2)(\sigma +1)} {}_{2}F_{1} \biggl(q \biggl(1+ \frac{1}{p_{1}} \biggr),2,\sigma +3,1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr] \\ &\qquad{} \times \biggl[\bigl(d^{p_{2}}\bigr)^{q (1+\frac{1}{p_{2}} )} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{2}} \biggr),1,2,1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr] \biggr), \\ &\varphi _{6}^{*}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}; \Omega \bigr) \\ &\quad=-\mu \biggl( \biggl\Vert \frac{1}{d^{p_{2}}}-\frac{1}{c^{p_{2}}} \biggr\Vert \biggr)^{\sigma } \biggl( \int _{0}^{1} \int _{0}^{1} \biggl[ \biggl[\frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{q (1+\frac{1}{p_{1}} )} \biggr] \\ &\qquad{} \times \biggl[ \bigl(r^{\sigma }(1-r)+r(1-r)^{\sigma } \bigr) \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{q (1+\frac{1}{p_{2}} )} \biggr]\,\mathrm{d}t\,\mathrm{d}r \biggr) \\ &\quad=-\mu \biggl( \biggl\Vert \frac{1}{d^{p_{2}}}-\frac{1}{c^{p_{2}}} \biggr\Vert \biggr)^{\sigma } \biggl( \biggl[\bigl(b^{p_{1}} \bigr)^{q (1+\frac{1}{p_{1}} )} {}_{2}F_{1} \biggl(q \biggl(1+ \frac{1}{p_{1}} \biggr),1,2,1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr] \\ &\qquad{} \times \biggl[ \frac{(d^{p_{2}})^{q (1+\frac{1}{p_{2}} )}}{(\sigma +1)(\sigma +2)} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{2}} \biggr),\sigma +1,\sigma +3,1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \\ &\qquad{} + \frac{(d^{p_{2}})^{q (1+\frac{1}{p_{2}} )}}{(\sigma +2)(\sigma +1)} {}_{2}F_{1} \biggl(q \biggl(1+ \frac{1}{p_{2}} \biggr),2,\sigma +3,1- \frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr] \biggr). \end{aligned}

VI. If we take $$\sigma =2$$ in Corollary 17, then

### Corollary 18

Under the assumptions of Corollary 17, if $$|\frac{\partial ^{2}f}{\partial r \,\partial t} |^{q}$$ is a two-dimensional harmonically strong $$(p_{1},h_{1})$$-$$(p_{2},h_{2})$$-convex function, where $$\frac{1}{p}+\frac{1}{q}=1$$ and $$q>1$$, then

\begin{aligned} & \bigl\vert \Xi \bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}},x,y: \Omega \bigr) \bigr\vert \\ &\quad\leq \frac{(b^{p_{1}}-a^{p_{1}})(d^{p_{2}}-c^{p_{2}})}{4p_{1}p_{2}a^{p_{1}}b^{p_{1}}c^{p_{2}}d^{p_{2}}(p+1)^{\frac{2}{p}}} \biggl[\varphi _{1}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,c) \biggr\vert ^{q} \\ &\qquad{} +\varphi _{2}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,c) \biggr\vert ^{q} + \varphi _{3}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(a,d) \biggr\vert ^{q} \\ & \qquad{}+\varphi _{4}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggl\vert \frac{\partial ^{2}f}{\partial r \,\partial t}(b,d) \biggr\vert ^{q} + \varphi _{5}^{**}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr)\\ &\qquad{}+ \varphi _{6}^{**}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}: \Omega \bigr) \biggr]^{\frac{1}{q}}, \end{aligned}

where $$\varphi _{1}(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}:\Omega ), \varphi _{2}(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}:\Omega ), \varphi _{3}(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}:\Omega ), \varphi _{4}(a^{p_{1}},b^{p_{1}}, c^{p_{2}},d^{p_{2}}:\Omega )$$ are given in Theorem 3, and

\begin{aligned} &\varphi _{5}^{**}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}; \Omega \bigr) \\ &\quad=-\mu \biggl( \biggl\Vert \frac{1}{b^{p_{1}}}-\frac{1}{a^{p_{1}}} \biggr\Vert \biggr)^{2} \biggl( \int _{0}^{1} \int _{0}^{1} \biggl[t(1-t) \biggl[ \frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{q (1+\frac{1}{p_{1}} )} \biggr] \\ &\qquad{} \times \biggl[ \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{q (1+ \frac{1}{p_{2}} )} \biggr]\, \mathrm{d}t\,\mathrm{d}r\biggr) \\ &\quad=-\mu \biggl( \biggl\Vert \frac{1}{b^{p_{1}}}-\frac{1}{a^{p_{1}}} \biggr\Vert \biggr)^{2} \biggl( [ \frac{(b^{p_{1}})^{q (1+\frac{1}{p_{1}} )}}{6} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{1}} \biggr),2,4,1-\frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \\ &\qquad{} \times \biggl[\bigl(d^{p_{2}}\bigr)^{q (1+\frac{1}{p_{2}} )} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{2}} \biggr),1,2,1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr] \biggr), \\ &\varphi _{6}^{*}\bigl(a^{p_{1}},b^{p_{1}},c^{p_{2}},d^{p_{2}}; \Omega \bigr) \\ &\quad=-\mu \biggl( \biggl\Vert \frac{1}{d^{p_{2}}}-\frac{1}{c^{p_{2}}} \biggr\Vert \biggr)^{2} \biggl( \int _{0}^{1} \int _{0}^{1} \biggl[ \biggl[\frac{a^{p_{1}}b^{p_{1}}}{(tb^{p_{1}}+(1-t)a^{p_{1}})} \biggr]^{q (1+\frac{1}{p_{1}} )} \biggr] \\ & \qquad{}\times \biggl[r(1-r) \biggl[ \frac{c^{p_{2}}d^{p_{2}}}{(rd^{p_{2}}+(1-r)c^{p_{2}})} \biggr]^{q (1+ \frac{1}{p_{2}} )} \biggr] \,\mathrm{d}t\,\mathrm{d}r \biggr) \\ &\quad=-\mu \biggl( \biggl\Vert \frac{1}{d^{p_{2}}}-\frac{1}{c^{p_{2}}} \biggr\Vert \biggr)^{2} \biggl( \biggl[\bigl(b^{p_{1}} \bigr)^{q (1+\frac{1}{p_{1}} )} {}_{2}F_{1} \biggl(q \biggl(1+ \frac{1}{p_{1}} \biggr),1,2,1- \frac{b^{p_{1}}}{a^{p_{1}}} \biggr) \biggr] \\ &\qquad{} \times \biggl[ \frac{(d^{p_{2}})^{q (1+\frac{1}{p_{2}} )}}{6} {}_{2}F_{1} \biggl(q \biggl(1+\frac{1}{p_{2}} \biggr),2,4,1-\frac{d^{p_{2}}}{c^{p_{2}}} \biggr) \biggr] \biggr). \end{aligned}

## 4 Conclusion

In this paper, we defined a new interesting class of functions, two-dimensional approximately harmonic $$(p_{1},h_{1})$$-$$(p_{2},h_{2})$$-convex function, and some Hermite–Hadamard type integral inequalities are provided as well on the coordinates. As a particular cases for $$p_{1},h_{1},p_{2},h_{2}$$, we get several new classes of functions. For instance, $$p_{1}=1=p_{2}$$ and $$h_{1}= h =h_{2}$$, we get the results of the paper [20] for approximately harmonic h-convex function. These results can be applied in convex analysis, optimization, and different areas of pure and applied sciences. The authors hope that these results will serve as a motivation for future work in this fascinating area.

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Correspondence to Wei Gao.

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Butt, S.I., Kashuri, A., Nadeem, M. et al. Approximately two-dimensional harmonic $$(p_{1},h_{1})$$-$$(p_{2},h_{2})$$-convex functions and related integral inequalities. J Inequal Appl 2020, 230 (2020). https://doi.org/10.1186/s13660-020-02495-6