Stability for the Mixed Type of Quartic and Quadratic Functional Equations.

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. [ABSTRACT FROM AUTHOR]