| Abstrakt: |
In this paper, we study an (A , Q) -functional equation f (x + y , z + w) + f (x + y , z − w) + f (x − y , z + w) + f (x − y , z − w) = 4 f (x , z) + 4 f (x , w) in a Banach space and determine its general solutions (in certain groups). Moreover, we verify some stability results of the (A , Q) -functional equation as a consequence of a fixed point theorem in a complete metric space investigated by Brzdȩk et al. [A fixed point approach to stability of functional equations, Nonlinear Anal. 74 (2011) 6728–6732]. [ABSTRACT FROM AUTHOR] |
