On the Brzdȩk’s fixed point approach to stability of a Drygas functional equation in 2-Banach spaces

Abstract

Using the Brzḑek’s fixed point approach, we will prove the generalized Hyers–Ulam–Rassias stability for the following Drygas functional equation in 2-Banach spaces $$\begin{aligned} f(x+y)+f(x-y)=2f(x)+f(y)+f(-y). \end{aligned}$$ Moreover, we investigate some hyperstability results for this equation.