Abstract
There is a strong correlation between convexity and symmetry concepts. In this study, we investigated the new generic class of functions called the –generalized convex and studied its basic algebraic properties. The Hermite–Hadamard inequality for the –generalized convex function, for the products of two functions and of this type, were proven. Moreover, this class of functions was applied to several known identities; midpoint-type inequalities of Ostrowski and Simpson were derived. Our results are extensions of many previous contributions related to integral inequalities via different convexities.
Keywords:
Hermite–Hadamard inequality; Ostrowski inequality; Simpson inequality; (n,m)–generalized convexity MSC:
26A33; 26A51; 26D07; 26D10; 26D15; 26D20
1. Introduction and Preliminaries
The twenty-first century began with the introduction and establishment of new tools used to solve linear and nonlinear differential and difference equations. In terms of the convexity theory, one important development involves defining a new class of convex functions, which is then tested on the well-known inequalities. “As it is known, inequalities aim to develop different mathematical methods. Nowadays, we need to seek accurate inequalities for proving the existence and uniqueness of the mathematical methods. In recent years, especially over the past two decades, several authors have been engaged in the study of inequalities, including various function classes (symmetric or asymmetric)”, see [1]. Moreover, the modern convexity theory has motivated researchers to propose a new generalized class of convex functions and to investigate their special models, which could effectively be used in different fields, in particular, agriculture, medicine, reliability engineering, demography, actuarial study, survival analysis, and others. Kasamsetty et al. in [2] defined a new class of convex functions used to delay modeling and established an application to the transistor sizing problem. Awan et al. in [3] obtained new classes of convex functions and inequalities. Hudzik and Maligranda in [4] investigated the class of s-convex functions. Eftekhari in [5] derived new results using –convexity in the second sense. Kadakal and İşcan in [6] established related inequalities via the exponential type convexity. Agarwal and Choi in [7] used fractional operators and found their image formulas. Rekhviashvili et al. in [8] described damped vibrations via a fractional oscillator model.
In much of the literature, we can see various Hermite–Hadamard () inequality types, in which one of the known classes of convex functions is utilized (e.g., [9,10,11]). Moreover, some generalizations of the integral inequalities, such as –Fejér, AB , midpoint , mid-end-point , conformable , and –Mercer integral inequalities are found (e.g., [12,13,14]). In addition, different integral inequalities using those convexities are investigated. Ujević in [15] obtained sharp inequalities for Simpson and Ostrowski types. Liu et al. in [16], using the –convexity class derived Ostrowski fractional inequalities. Kaijser et al. in [17] established Hardy-type inequalities via convexity. Rashid et al. in [18], using generalized k–fractional integrals, found Grüss inequalities. For more recent published papers on , see [19,20].
Let us review some fundamental and preliminary results on convexity and inequality.
Definition 1.
Function is called convex, if
holds for all (τ is an interval with real numbers and is the set of real numbers) and . Moreover, Θ is concave if is convex.
Definition 2
([4]). Let be a real number. A function is called s-convex (in the second sense), if
holds for all , and .
Definition 3
([21]). Let be intervals in and let be a nonnegative function, and . A nonnegative function is called h-convex, if
holds for all
Toply et al. [22] introduced the following class of convex functions:
Definition 4.
Let A function is called n–polynomial convex, if
holds for every and .
Recently, Rashid et al. [23] defined the following class of convex functions:
Definition 5
([23]). Assume that and A function is said to be n–polynomial s–type convex, if
holds for every and .
The following double inequality, namely the inequality, is remarkable, and it played an important role in the analysis.
Theorem 1
( inequality [24]). Let be a convex function on τ for and then
The following well-known inequality is called the Ostrowski inequality:
Theorem 2
(Ostrowski inequality [16]). Let a differentiable function in the interval τ and let with If for all then
Another type of inequality is obtained by Dragomir et al. [25], which is as follows:
Theorem 3
(Simpson inequality [25]). Assume that is a four-time continuous and differentiable function on such that with then
For brevity, we denote by the convex set in the sequel.
Motivated by the above results, we introduce the following generic class of convex functions:
Definition 6.
Suppose that , where , and assume that are continuous functions for all and . A function , which is nonnegative, is said to be –generalized convex with respect to if
holds for every and .
Remark 1.
From Definition 6, we can observe that:
- 1.
- If and then we have Definition 1.
- 2.
- If and then we obtain Definition 2.
- 3.
- If and then we obtain Definition 3.
- 4.
- If and then we obtain Definition 4.
- 5.
- If and then we obtain Definition 5.
Interested readers can derive many other known and unknown classes for suitable choices of the above functions and
This article is divided into five sections: in Section 2, algebraic properties of the –generalized convex function are presented. In Section 3, a new version of the inequality is presented; by using this definition, we will also derive the products of two functions of this type. In Section 4, we obtain general results by using the well-known identities of midpoint-type inequalities of Ostrowski and Simpson for our new defined convex functions; we obtain special cases from these. Section 5 concludes the article.
2. Algebraic Properties of the New Convex Function
This section deals with algebraic properties of our new definition.
Theorem 4.
Suppose that , where , and assume that are continuous functions for all and , and If , and are three nonnegative –generalized convex functions with respect to then
- 1.
- is the –generalized convex with respect to ;
- 2.
- is the –generalized convex with respect to for any nonnegative real number c.
Proof.
The proof is evident, so we omit it. □
Theorem 5.
Suppose that , where , and assume that are continuous functions for all and . Let be a convex function and is a non-decreasing and nonnegative –generalized convex function with respect to Then the function is an –generalized convex with respect to
Proof.
For all and we have
which ends our proof. □
Theorem 6.
Suppose that , where , and assume that are continuous functions for all and . Let be a family of nonnegative –generalized convex functions with respect to and . Then Θ is an –generalized convex function with respect to and is an interval.
Proof.
Let and then
which ends our proof. □
Theorem 7.
Suppose that , where , and assume that are continuous functions for all and . If is a nonnegative –generalized convex function with respect to then Θ is bounded on
Proof.
Let and . Then, there exists , such that . Moreover, since are continuous functions on for all and then we denote, respectively, and Hence,
Moreover, for all there exists , such that or Let us suppose that without loss of generality. So, we have
By making use of M as the upper bound, we can deduce
which ends our proof. □
3. The Inequality for the New Convex Function
In this section, we will establish some integral inequalities of the -type pertaining to the –generalized convex functions.
Theorem 8.
Assume that , where , and assume that are continuous functions for all and . If is a nonnegative –generalized convex function with respect to then we have
where
Proof.
Let Applying the –generalized convexity with respect to of on we have
Let us denote, respectively, and From inequality (11), we obtain
Integrating on both sides (12), with respect to from 0 to we obtain
which gives the proof of the left hand side of (10). For the right hand side of (10), we use the definition of –generalized convexity with respect to of where Hence,
and
Adding both of them, we have
Integrating on both sides (13) with respect to from 0 to we obtain
which leads to
which ends our proof. □
Remark 2.
We have particular cases from Theorem 8:
- If and for all and , we have Theorem 1.
- If , and for , and , we obtain ([23], Theorem 2.1).
- If , and for all and , we obtain ([22], Theorem 4).
Theorem 9.
Let and where Assume that are continuous functions for all and If are nonnegative and –generalized convex functions with respect to
, and
respectively, then we have
where
and
4. Further Results
We denote by the set of all integrable functions on Let us recall the following lemmas in order to establish our following results.
Lemma 1
(Midpoint identity [26]). Let be a differentiable function on τ and with If then
Lemma 2
(Ostrowski identity [27]). Let be a differentiable function on τ and with If then
Lemma 3
(Simpson identity [28]). Let be a differentiable function on τ and with If then
Theorem 10.
Suppose that , where , and assume that are continuous functions for all and , and be a differentiable function on such that If is an –generalized convex function with respect to on then we have
where
Proof.
By using Lemma 1 and the –generalized convexity of with respect to , we have
which ends our proof. □
Corollary 1.
We have particular cases from Theorem 10:
- If and for all and , we obtain
- If and for all and , we obtain
- If and for all , and , we obtain
Theorem 11.
Suppose that , where , and assume that are continuous functions for all and , and be a differentiable function on , such that If is an –generalized convex function with respect to on , then for and , we have
where
Proof.
By using Lemma 1, Hölder’s inequality and the –generalized convexity of with respect to , we have
which ends our proof. □
Corollary 2.
We have particular cases from Theorem 11:
- If and for all and , we have
- If and for all and , we obtain
- If and for all , and , we obtain
Theorem 12.
Suppose that , where , and assume that are continuous functions for all and , and be a differentiable function on , such that If is an –generalized convex function with respect to on , then for we have
where and are defined as in Theorem 10.
Proof.
By using Lemma 1, the well-known power mean inequality and the –generalized convexity of with respect to , we have
which ends our proof. □
Corollary 3.
We have particular cases from Theorem 12:
- If and for all and , we obtain
- If and for all and , we obtain
- If and for all , and , we obtain
Theorem 13.
Suppose that , where , and assume that are continuous functions for all and , and be a differentiable function on , such that If is an –generalized convex function with respect to on then we have
where
Proof.
By using Lemma 2 and the –generalized convexity of with respect to , we have
which ends our proof. □
Corollary 4.
We have particular cases from Theorem 13:
- If and for all and , we obtain
- If and for all and , we obtain
- If and for all , and , we obtain
Theorem 14.
Suppose that , where , and assume that are continuous functions for all and , and be a differentiable function on such that If is –generalized convex function with respect to on then for and we obtain
where and are defined as in Theorem 8.
Proof.
By using Lemma 2, Hölder’s inequality and the –generalized convexity of with respect to , we obtain
which ends our proof. □
Corollary 5.
We have particular cases from Theorem 14:
- If and for all and , we obtain
- If and for all and , we obtain
- If and for all , and , we obtain
Theorem 15.
Suppose that , where , and assume that are continuous functions for all and , and be a differentiable function on , such that If is the –generalized convex function with respect to on then for we have
where and are defined as in Theorem 13.
Proof.
By using Lemma 2, the well-known power mean inequality and the –generalized convexity of with respect to , we have
which ends our proof. □
Corollary 6.
We have particular cases from Theorem 15:
- If and for all and , we obtain
- If and for all and , we obtain
- If and for all , and , we obtain
Theorem 16.
Suppose that , where , and assume that are continuous functions for all and , and be a differentiable function on , such that If is the –generalized convex function with respect to on then we have
where
and
for all and .
Proof.
By using Lemma 3 and the –generalized convexity of with respect to , we have
which ends our proof. □
Corollary 7.
If we take and in Theorem 16, we obtain
where
and
Theorem 17.
Suppose that , where , and assume that are continuous functions for all and , and be a differentiable function on such that If is the –generalized convex function with respect to on then for and we have
where and are as defined in Theorem 8.
Proof.
By using Lemma 3, Hölder’s inequality and the –generalized convexity of with respect to , we have
which ends our proof. □
Corollary 8.
We have particular cases from Theorem 17:
- If and for all and , we obtain
- If and for all and , we obtain
- If and for all , and , we obtain
Theorem 18.
Suppose that , where , and assume that are continuous functions for all and , and be a differentiable function on , such that If is the –generalized convex function with respect to on then for we have
where , and for all are defined as in Theorem 16.
Proof.
By using Lemma 3, the well-known power mean inequality and –generalized convexity with respect to , we have
which ends our proof. □
Corollary 9.
If we take and in Theorem 18 for all and , we obtain
where and for all are as defined in Corollary 7.
5. Conclusions
In this article, we studied algebraic properties of a new generic class of functions called the –generalized convex function; based on this, we proposed inequalities. Moreover, we obtained new midpoint-type inequalities of Ostrowski and Simpson based on our new definition, using well-known integral identities. Finally, we observed that the new, defined convex function is a powerful type of function used to investigate various inequalities in the real analysis field.
Author Contributions
Conceptualization, A.K. and P.O.M.; methodology, A.K., R.P.A. and P.O.M.; software, K.N.; K.M.A. and Y.S.H.; validation, A.K., P.O.M. and Y.S.H.; formal analysis, R.P.A., P.O.M., K.N. and K.M.A.; investigation, A.K., P.O.M. and Y.S.H.; resources, P.O.M., K.N. and K.M.A.; data curation, K.N. and Y.S.H.; writing—original draft preparation, A.K., P.O.M. and R.P.A.; writing—review and editing, A.K., P.O.M., K.M.A. and Y.S.H.; visualisation, A.K., R.P.A. and P.O.M.; supervision, R.P.A., P.O.M., K.N. and Y.S.H.; project administration, P.O.M. and K.N.; funding acquisition, K.N. All authors have read and agreed to the published version of the manuscript.
Funding
Not applicable.
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
Not applicable.
Acknowledgments
This Research was supported by Taif University Researchers Supporting Project Number (TURSP2020/217), Taif University, Taif, Saudi Arabia, and the National Science, Research, and Innovation Fund (NSRF), Thailand.
Conflicts of Interest
The authors declare no conflict of interest.
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