doi:10.1155/2009/923476 Research Article On the Generalized Hyers-Ulam-Rassias Stability of Quadratic Functional Equations

We achieve the general solution and the generalized Hyers-Ulam-Rassias and Ulam-Gavruta-Rassias stabilities for quadratic functional equations fax by fax − by ba b/2fx y ba b/2fx −y 2a2 − ab − b2fx b2 − abfywhere a, b are nonzero fixed integers with b / ±a,−3a, and faxbyfax−by 2a2fx2b2fy for fixed integers a, bwith a, b / 0 and a ± b / 0. Copyright q 2009 M. E. Gordji and H. Khodaei. 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. 1