“…The stability of a general quadratic function equation was obtained by Y. H. Lee [11], Y. H. Lee et al [12], and S. S. Jin et al [13]. On the other hand, the stability of a general cubic function equation was studied by Y. H. Lee [14,15], S. M. Jun et al [16], and Y. H. Lee et al [17,18], and the stability of the general quartic function equation are discussed in Y. H. Lee [20] and Y. H. Lee et al [?,18,21,22,23]. Moreover, the stability of a general quintic functional equation has been studied by S. S. Jin et al [24], and the stability of the general sextic function equation has been obtained by Y. H. Lee [25], I.…”