Abstract
In this work, we established new inequalities of Hermite–Hadamard type for convex functions via conformable fractional integrals. Through the conformable fractional integral inequalities, we found some new inequalities of Hermite–Hadamard type for convex functions in the form of classical integrals.
1. Introduction
A function is said to be convex on the interval , if the inequality
holds for all and . We say that h is concave if is convex.
For convex functions, many equalities or inequalities have been established by many authors; for example the Ostrowski type inequality [1], Hardy type inequality [2], Olsen type inequality [3], and Gagliardo–Nirenberg type inequality [4] but the most common and significant inequality is the Hermite–Hadamard type inequality [5,6], which is defined as:
where the function is assumed to be a convex function with and .
A number of mathematicians in the field of applied and pure mathematics have dedicated their efforts to extend, generalize, counterpart, and refine the Hermite–Hadamard inequality (2) for different classes of convex functions and mappings. For more recent results obtained on inequality (2), we refer the reader to References [5,7,8,9,10].
Definition 1
([11]). Suppose that . The left and right Riemann–Liouville fractional integrals and of order are defined by
and
respectively, where is the standard gamma function defined by and .
As for classical integrals, many Hermite–Hadamard type inequalities have been established for the Riemann–Liouville fractional integrals; for more details and interesting applications see References [6,12,13].
Now, we give the definition of the conformable fractional derivative with its important properties which are useful in order to obtain our main results (see References [14,15,16,17,18,19,20,21]). In our study, we use the Katugampola derivative formulation of conformable derivative which is explained in the following definition:
Definition 2
([20]). Given a function . Then, the conformable fractional derivative of h of order α of h at ζ is defined by
If h is -differentiable in some , exist, then define
Additionally, note that if h is differentiable, then
We can write for or to denote the conformable fractional derivatives of h of order at . In addition, if the conformable fractional derivative of h of order exists, then we simply say h is -differentiable.
Theorem 1
([20]). Let and be α-differentiable at a point . Then,
- 1.
- for all ,
- 2.
- ,
- 3.
- ,
- 4.
- for all constant function ,
- 5.
- ,
- 6.
- .
Now, we give the definition of conformable fractional integral:
Definition 3
([16]). Let and . We say that a function is α-fractional integrable on , if the integral
exists and is finite.
Remark 1.
(u) All α-fractional integrable functions on are indicated by .
(v) For the usual Riemann improper integral and , we have
The aim of our article is to establish some new inequalities connected with the Hermite–Hadamard inequalities (2) via conformable fractional integral.
2. Main Results
Our main results depend on the following equality:
Lemma 1.
Let be an α-fractional differentiable mapping on with . If , then the following identity for conformable fractional integral holds:
where
and
Proof.
By using the definition of the conformable fractional derivative (4), we have
On integrating by parts, one can have
Using the change of the variable and definition of conformable fractional integral (5), we obtain
Similarly, we get
and
Adding and together, we obtain the desired identity (7). This completes the proof of Lemma 1. □
Remark 2.
With the similar assumptions of Lemma 1, if , then identity (7) reduces to the following identity:
where
which is obtained by Shi et al. [12].
Theorem 2.
Let be an α-fractional differentiable mapping on with . If and is convex on , then the following inequality for conformable fractional integral holds:
where
Proof.
Using Lemma 1 and the property (4), we have
By using the convexity of for , we have
and
Since is convex on for any , so (17) becomes
Simple calculation gives
This completes the proof of Theorem 2. □
Corollary 1.
With the similar assumptions of Theorem 2, if , then
Theorem 3.
Let be an α-fractional differentiable mapping on with . If and is convex on , then the following inequality for conformable fractional integral holds:
where
Proof.
Using Lemma 1 and the property (4), we have
It follows from the power–mean inequality that
Since is convex on for any , we obtain
where we have used the facts that
and
Analogously
and
Corollary 2.
With the similar assumptions of Theorem 3, if , then
Theorem 4.
Let be an α-fractional differentiable mapping on with . If and is concave on , then the following inequality for conformable fractional integral holds:
where , and are given in Theorem 3 and
Proof.
By using the power–mean inequality and the concavity of for any , we have
This implies that
This means that is also concave. Using inequality (20) in (18) and then applying the Jensen’s integral inequality, we get
where we have used the facts that
Similarly, we get , and .
Corollary 3.
With the similar assumptions of Theorem 4, if , then
where
and
3. Conclusions
In this work, we have established new conformable fractional integral inequalities of Hermite–Hadamard type for convex functions. As a special case, if we substitute into the general definition of conformable fractional integrals (Definition 2), we obtain the classical integrals. In view of this, we obtained some new inequalities of Hermite–Hadamard type for convex functions involving classical integrals.
Author Contributions
The authors contributed equally to this work. All authors read and approved the final manuscript.
Funding
This research received no external funding.
Acknowledgments
The authors are thankful to the anonymous referees for their careful corrections to and valuable comments on the original version of this paper.
Conflicts of Interest
The authors declare no conflict of interest.
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