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Abstract
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Fixed Point Theory and Applications
Volume 2008 (2008), Article ID 493751, 9 pages
doi:10.1155/2008/493751

Generalized Hyers-Ulam stability of quadratic functional equations: a fixed point approach

Choonkil Park

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

Abstract

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(x−y) in Banach spaces.