The stability of the quartic functional equation in various spaces

On the Stability of the Orthogonally Quartic Functional Equation

Intuitionistic fuzzy stability of a quadratic and quartic functional equation

In this paper, we prove the generalized Hyers--Ulamstability of a quadratic and quartic functional equation inintuitionistic fuzzy Banach spaces.

The stability of the cubic functional equation in various spaces

We prove the stability of the cubic functional equation f(2x + y) + f(2x− y) = 2f(x + y) + 2f(x− y) + 12f(x) in the setting of various spaces. AMS subject classifications: Primary 46S40, 39B82, 54E40

on the stability of the orthogonally quartic functional equation

Hyers-Ulam-Rassias stability of a composite functional equation in various normed spaces

In this paper, we prove the generalized Hyers-Ulam(or Hyers-Ulam-Rassias ) stability of the following composite functional equation f(f(x)-f(y))=f(x+y)+f(x-y)-f(x)-f(y) in various normed spaces.