APPROXIMATE QUADRATIC FUNCTIONAL EQUATION IN FELBIN’S TYPE NORMED LINEAR SPACES

Abstract

In this paper, we prove the generalized Hyers–Ulam–Rassias stability ofquadratic functional equation in Felbin’s type normed linear spaces byusing the direct and fixed point methods. The concept of Hyers-UlamRassias stability originated from Th. M. Rassias’ stability theorem thatappeared in his paper: On the stability of the linear mapping in Banachspaces, Proc. Amer. Math. Soc. 72 (1978), 297–300.