International Journal of Engineering, Science and Mathematics
Vol.7 Special Issue 4(1), April 2018,
ISSN: 2320-0294 Impact Factor: 6.765
Journal Homepage: http://www.ijmra.us, Email: editorijmie@gmail.com Double-
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8
International Journal of Engineering, Science and Mathematics
http://www.ijmra.us, Email: editorijmie@gmail.com
Stability of Pexiderized Functional Equation in Complex
Banach Spaces: A Fixed-Point Approach
Parbati Saha
Pratap Mondal
Abstract
The study of Hyers-Ulam-Rassias stability for several functional equations has
been wildly spreaded in the context of different areas of mathematics and such
type stability in real Banach spaces along with its several extensions has been
examined by a number of mathematicians. In this paper we prove the Hyers-
Ulam-Rassias stability of a Pexiderized functional equation in complex
Banach spaces under suitable conditions.
Keywords:
Hyers-Ulam stability;
Pexider type functional
equation;
Complex Banach spaces;
Alternative fixed-point
theorem.
Copyright © 2018 International Journals of Multidisciplinary Research
Academy.All rights reserved.
Author correspondence:
Department of Mathematics,
Bijoy Krishna Girls’ College, Howrah
Howrah, West Bengal, India-711101
Email: pratapmondal111@gmail.com
1. Introduction
The idea of stability of functional equations, in particular, about the stability of group homomorphism, was
first posed by Ulam [15] and it was first partially answered by Hyers [7] for Banach spaces. Aoki [1]
generalized the result of Hyers for additive mapping and it was further generalized by Rassias [14] for linear
mappings by considering an unbounded Cauchy difference. A generalization of the Rassias theorem was
obtained by Gavruta [6] by replacing the unbounded Cauchy difference with a general control function in the
spirit of Rassias’ approach. A number of outcomes regarding the stability problems of various functional
equations have been extensively investigated by a number of researchers [3, 5, 8, 9, 10, 11].
In this paper we prove the Hyers-Ulam-Rassias stability for Pexiderized functional equation ሺ ݔ+ݕሻ=
ሺݔሻ − ℎሺݕሻ in complex Banach spaces by using the fixed-point method and examine a property of the solution
of the above functional equation in technical terms.
2. Mathematical Background
First, we describe the notion of Pexiderized additive functional equation.
A mapping : → is said to be an additive form if ሺݔሻ= ݔfor all ,ݔ∈.
If and are assumed to be a real vector space and a Banach space respectively then for a mapping
: → , consider a functional equation
ሺ ݔ+ ݕሻ = ሺݔሻ + ሺݕሻ . . . ሺʹ.ͳሻ.
which is known as the Cauchy functional equation and any solution of ሺʹ.ͳሻ is termed as an additive mapping.
Particularly, if = = , the additive form ሺݔሻ= ݔis a solution ofሺʹ.ͳሻ.
Department of Mathematics, Indian Institute of Engineering Science
and Technology, Shibpur, Howrah - 711103, West Bengal, India.
Department of Mathematics, Bijoy Krishna Girls’ College, Howrah, Howrah-711101, West Bengal, India.