Journal of Inequalities and Applications
Volume 2010 (2010), Article ID 472721, 8 pages
Research Article

Approximate Behavior of Bi-Quadratic Mappings in Quasinormed Spaces

1Department of Mathematics Education, College of Education, Mokwon University, Daejeon 302-729, Republic of Korea
2College of Liberal Arts, Kyung Hee University, Yongin 446-701, Republic of Korea

Received 27 April 2010; Accepted 18 June 2010

Academic Editor: Radu Precup

Copyright © 2010 Won-Gil Park and Jae-Hyeong Bae. 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.


We obtain the generalized Hyers-Ulam stability of the bi-quadratic functional equation f(x+y,z+w)+f(x+y,z-w)+f(x-y,z+w)+f(x-y,z-w)=4[f(x,z)+f(x,w)+f(y,z)+f(y,w)] in quasinormed spaces.