Stability for the Mixed Type of Quartic and Quadratic Functional Equations

Abstract

We establish the general solutions of the following mixed type of quartic and quadratic functional equation: f(2x+y)+f(2x-y)=4f(x+y)+4f(x-y)+2f(2x)-8f(x)-6f(y). Moreover we prove the Hyers-Ulam-Rassias stability of this equation under the approximately quartic and the approximately quadratic conditions.