Hyers-Ulam stability of additive set-valued functional equations

Abstract

In this paper, we define the following additive set-valued functional equations f(alpha chi + beta y) = rf (chi) sf (y), (1) f(x + y + z) = 2f (x + y/2) + f(z) (2) for some real numbers alpha > 0, beta > 0, r, s is an element of R with alpha + beta = r + s not equal 1, and prove the Hyers-Ulam stability of the above additive set-valued functional equations.