“…The case of approximately additive functions was solved by Hyers [6] under the assumption that G 1 and G 2 are Banach spaces. Later, the result of Hyers was generalized by Rassias [14] and other mathematicians (see [3,4,5,7,8,9,10,11,12,15,16,17,19,20]). The work of Rassias stimulated a number of mathematicians to investigate the stability problem of various functional equations.…”