On the Hyers–Ulam–Rassias stability of an additive functional equation in quasi-Banach spaces

In this paper we investigate the Hyers–Ulam–Rassias stability of the following functional equation: m i=1 f mxi + m j=1, j =i x j + f m i=1 xi = 2 f m i=1 mxi (m ∈ N, m 2) in quasi-Banach spaces.