The hyperstability of AQ-Jensen functional equation on 2-divisible abelian group and inner product spaces

Abstract

In this paper, we prove the hyperstability of the following mixed additive-quadratic-Jensen functional equation 2f(x+y2)+f(x−y2)+f(y−x2)=f(x)+f(y)$$2f({{x + y} \over 2}) + f({{x - y} \over 2}) + f({{y - x} \over 2}) = f(x) + f(y)$$ in the class of functions from an 2-divisible abelian group G into a Banach space.

Keywords

• hyperstability
• additive-quadratic-jensen functional equation
• fixed point theorem