STABILITY OF A FUNCTIONAL EQUATION IN COMPLEX BANACH SPACES

Abstract

Using fixed point technique, in the present paper , we wish to examine generalization of the Hyers-Ulam-Rassias stability theorem for the functional equations f 2 x + i y + f x + 2 i y = 4 f x + i y + f x + f y 0.1 and f 2 x + i y − f i x − 2 y = − 4 f i x − y + f x − f − y 0.2 in complex Banach spaces .