Abstract. In this paper, the authors obtain the generalized Ulam -Hyers stability of a 2 -variable AC -mixed type functional equationin Felbin's type spaces using fixed point method.Mathematics Subject Classification: 39B52, 32B72, 32B82

In this paper, we have established the general solution and generalized Ulam -Hyers stability of the following nonic functional equationwhere 9! = 362880 in a Banach Space (BS), Felbin's type Fuzzy Normed Space (FFNS) and Intuitionistic Fuzzy Normed Space (IFNS) using the standard direct and fixed point method.

In this paper, authors proved the generalized Ulam -Hyers stability of system of additive functional equations f n

In this paper, we achieve the general solution and generalized Ulam - Hyers stability of a $n$-dimensional additive-quadratic-cubic-quartic (AQCQ) functional equation$$\begin{aligned}f\left(\sum_{i=1}^{n-1} v_i+2 v_n\right)+f\left(\sum_{i=1}^{n-1} v_i-2 v_n\right)= & 4 f\left(\sum_{i=1}^n v_i\right)+4 f\left(\sum_{i=1}^{n-1} v_i-v_n\right)-6 f\left(\sum_{i=1}^{n-1} v_i\right) \\& +f\left(2 v_n\right)+f\left(-2 v_n\right)-4 f\left(v_n\right)-4 f\left(-v_n\right)\end{aligned}$$where $n$ is a positive integer with $n \geq 3$ in Banach Space (BS) via direct and fixed point methods. The stability results are discussed in two different ways by assuming $n$ is an odd positive integer and $n$ is an even positive integer.

In this paper, we establish the various Ulam stability of a alternate additive-quadratic functional equation in Intuitionistic Fuzzy Banach spaces via two different substitutions.