On stability of a cubic functional equation in intuitionistic fuzzy normed spaces

In this paper, we determine some stability results concerning the cubic functional equation f ð2x þ yÞ þ f ð2x yÞ ¼ 2f ðx þ yÞ þ 2f ðx yÞ þ 12f ðxÞ in intuitionistic fuzzy normed spaces (IFNS). We define the intuitionistic fuzzy continuity of the cubic mappings and prove that the existence of a solution for any approximately cubic mapping implies the completeness of IFNS.