Fixed Point Theory and Applications
Volume 2008 (2008), Article ID 493751, 9 pages
Research Article

Generalized Hyers-Ulam Stability of Quadratic Functional Equations: A Fixed Point Approach

Choonkil Park

Department of Mathematics, Hanyang University, Seoul 133-791, South Korea

Received 6 September 2007; Revised 19 November 2007; Accepted 15 February 2008

Academic Editor: Thomas Bartsch

Copyright © 2008 Choonkil Park. 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.


Using the fixed point method, we prove the generalized Hyers-Ulam stability of the quadratic functional equation f(2x+y)=4f(x)+f(y)+f(x+y)f(xy) in Banach spaces.