Advances in Difference Equations
Volume 2009 (2009), Article ID 256165, 10 pages
doi:10.1155/2009/256165
Research Article

A Fixed Point Approach to the Stability of a Quadratic Functional Equation in C∗-Algebras

Mohammad B. Moghimi,1 Abbas Najati,1 and Choonkil Park2

1Department of Mathematics, Faculty of Sciences, University of Mohaghegh Ardabili, 56199-11367 Ardabil, Iran
2Department of Mathematics, Research Institute for Natural Sciences, Hanyang University, Seoul 133-791, South Korea

Received 18 May 2009; Accepted 31 July 2009

Academic Editor: Tocka Diagana

Copyright © 2009 Mohammad B. Moghimi et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

We use a fixed point method to investigate the stability problem of the quadratic functional equation f(x+y)+f(x−y)=2f(xx∗+yy∗) in C∗-algebras.