A FIXED POINT APPROACH TO THE INTUITIONISTIC FUZZY STABILITY OF QUINTIC AND SEXTIC FUNCTIONAL EQUATIONS

Abstract. The fixed point alternative methods are implemented to give Hyers- Ulam stability for the quintic functional equation f(x + 3y) - 5f(x + 2y) + 10f(x+y)-10f(x)+5f(x-y)-f(x-2y) = 120f(y) and the sextic functional equation f(x + 3y) - 6f(x + 2y) + 15f(x + y) - 20f(x) + 15f(x - y) - 6f(x -2y) + f(x - 3y) = 720f(y) in the setting of intuitionistic fuzzy normed spaces (IFN-spaces). This method introduces a metrical context and shows that the stability is related to some fixed point of a suitable operator. Furthermore, the interdisciplinary relation among the fuzzy set theory, the theory of intu- itionistic spaces and the theory of functional equations are also presented in the paper.