On the Stability of a Generalized Quadratic and Quartic Type Functional Equation in Quasi-Banach Spaces

Abstract

We establish the general solution of the functional equation f(nx + y) + f(nx - y) = n(2)f(x - y) + 2(f(nx) - n(2)f(x)) -2(n(2) - 1)f(y) for fixed integers n with n not equal 0,+/- 1 and investigate the generalized Hyers-Ulam stability of this equation in quasi-Banach spaces. Copyright (C) 2009 M. Eshaghi Gordji et al.