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

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

Mohammad B. Moghimi1 , Abbas Najati1 and Choonkil Park3

1Department of Mathematics, Faculty of Sciences, University of Mohaghegh Ardabili, 56199-11367 Ardabil, Iran
3Department of Mathematics, Research Institute for Natural Sciences, Hanyang University, Seoul 133-791, South Korea

Abstract

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