Abstract and Applied Analysis
Volume 2009 (2009), Article ID 535678, 17 pages
doi:10.1155/2009/535678

Fuzzy stability of Jensen-type quadratic functional equations

Sun-Young Jang1 , Jung Rye Lee2 , Choonkil Park3 and Dong Yun Shin4

1Department of Mathematics, University of Ulsan, Ulsan 680-749, South Korea
 2Department of Mathematics, Daejin University, Kyeonggi 487-711, South Korea
 3Department of Mathematics, Hanyang University, Seoul 133-791, South Korea
 4Department of Mathematics, University of Seoul, Seoul 130-743, South Korea

Abstract

We prove the generalized Hyers-Ulam stability of the following quadratic functional equations 2f((x+y)/2)+2f((x−y)/2)=f(x)+f(y) and f(ax+ay)+(ax−ay)=2a2f(x)+2a2f(y) in fuzzy Banach spaces for a nonzero real number a with a≠±1/2.