1
1 Introduction
If
is a convex mapping and
,
with
, then one has
(1.1)
The subsequent inequality is an improvement of the inequality (1.1).
(1.2)
Many different generalizations, new extensions and improvements related to the inequality (1.1) can be found in Awan et al. (2016), Chu et al. (2016, 2017), Du et al. (2017), Iqbal et al. (2018), İşcan et al. (2016), Khan et al. (2017a,b,c), Khan et al. (2018a,b,c), Sarikaya and Karaca (2014), Set et al. (2016), Xi et al. (2015).
Let us consider an invex set
. A set
is named invex set with respect to the mapping
, if
holds, for all
and
. A mapping
is called preinvex respecting
, if the following inequality:
(1.3)
grips, for every
and
.
The preinvex function is an important substantive generalization of the convex function.
Example 1.1
The function
,
with respect to the following
(1.4)
is preinvex on
while it is not convex on
.
This paper aims to obtain estimation type results related to k-fractional integral operators. For this, we suppose that the absolute value of the derivative of the considered mapping is preinvex. Next, we substitute this hypothesis with the boundedness of the derivative and with a Lipschitzian condition for the derivative of the considered mapping to derive integral inequalities with new bounds. Applications of our results to random variables are also provided.
We end this section by reciting a well-known k-fractional integral operators in the literature.
Definition 1.1
Let
, the k-fractional integrals
and
of order
are defined by
and
respectively, where
, and
is the k-gamma function defined as
,
, with the properties
and
.
2
2 Main results
Throughout this work, let
be an open invex subset respecting
and
with
, and let
be a differentiable mapping such that
is integrable on the
-path
with
. Before stating the results, we use notations below.
(2.1)
If
with
, then we have
(2.2)
Choosing
and
, the Eq. (2.2) reduces to
Specially,
Choosing
and
, the Eq. (2.2) degenerates into
Specially,
We need the following lemma for our results.
Lemma 2.1
One has the subsequent identity
(2.3)
for k-fractional integrals with
,
,
and
.
Proof
Using integration by parts and appropriate substitutions, such as
, we can obtain the identity (2.3). □
Example 2.1
If we take
,
,
, and
(2.4)
then all the assumptions in Lemma 2.1 are satisfied. Clearly, the left of the Eq. (2.3) is
and the right of the Eq. (2.3) is
Corollary 2.1
If
with
in Lemma 2.1, then one has
(2.5)
which is a new form of Lemma 2.1.
Theorem 2.1
If
for
is preinvex on
, then the coming inequality for k-fractional integrals with
,
,
,
and
grips:
(2.6)
where
(2.7)
Proof
According to Lemma 2.1, the Holder inequality and preinvexity of
, one gets
where
When
, we have
when
, we have
when
, we have
The above inequality is obtained by using the fact that
The proof of Theorem 2.1 is completed. □
Corollary 2.2
Choosing
,
and
for
in Theorem 2.1, one obtains
(2.8)
Specially, putting
and
, one has
(2.9)
The second inequality is obtained by applying the convexity of
and the succeeding fact that
Theorem 2.2
If
for
is preinvex on
, then the coming inequality for k-fractional integrals with
,
,
and
grips:
(2.10)
where
(2.11)
and
(2.12)
Proof
Using Lemma 2.1 and the power mean inequality, one has
where
These last four inequalities clasp due to the preinvexity of
. This ends the proof.
Corollary 2.3
Choosing
,
and
with
in Theorem 2.2, one obtains
(2.13)
Specially, taking
,
and utilizing similar arguments as in Corollary 2.2, one gets
(2.14)
Remark 2.2
Theorems 2.1 and 2.2 will be reduced to Theorem 2 and 3 in Latif (2015), respectively, if we choose
,
and
for
.
3
3 New estimation results
For obtaining new estimation type results, we deal with the boundedness and the Lipschitzian condition of
, respectively.
Theorem 3.1
Assume that there exists constants
such that
for all
, then the inequality
(3.1)
holds with
,
,
and
.
Proof
From Lemma 2.1, we have
Using the fact that
, one obtains
(3.2)
The proof is completed. □
Corollary 3.1
In Theorem 3.1, choosing
for
, and
, one gets
(3.3)
Remark 3.1
Taking
in Corollary 3.1, one can see the following.
(a) For
, we have
(3.4)
(b) For
, we have
(3.5)
(c) For
, we have
(3.6)
Theorem 3.2
Assume that
satisfies Lipschitz condition on
for some
, then the inequality
(3.7)
grips for all
,
,
and
.
Proof
From Lemma 2.1, we have
Utilizing the fact that
satisfies Lipschitz condition on
for
, we have
where
After a simple calculation, we obtain the desired result. □
Corollary 3.2
In Theorem 3.2, choosing
for
, and
, one has
(3.8)
Remark 3.2
Putting
in Corollary 3.2, one can see the following.
(a) For
, we have
(3.9)
(b) For
, we have
(3.10)
(c) For
, we have
(3.11)