HYERS-ULAM STABILITY OF A GENERAL DIAGONAL SYMMETRIC FUNCTIONAL EQUATION
Using the direct method and the fixed point method, we prove the Hyers-Ulam stability for the symmetric functional equation f(phi(1)(x,y,z)) = phi(2)(f(x), f(y), f(z)) in Banach spaces. As a consequence, we obtain some stability results in the sense of Hyers-Ulam-Rassias.
functional equation fixed point hyers-ulam-rassias stability