The main aim of this paper is to establish the Hyers–Ulam stability and hyperstability of a
Jensen-type quadratic mapping in 2-Banach spaces. That is, we prove the various types of …

For the inner product space, we have Appolonius' identity. From this identity, Park and Th. M.
Rassias induced and investigated the quadratic functional equation of the Apollonius type …

In this paper, we introduce and solve a system of bi-Drygas functional equations\begin
{equation}\left\{\begin {aligned} &f (x+ y, z)+ f (xy, z)= 2f (x, z)+ f (y, z)+ f (-y,-z)\nonumber\\&f …

The main aim of this paper is to establish the generalized Hyers-Ulam stability of a bi-
quadratic mappings in non-Archimedean spaces. That is, we prove the generalized Hyers …

In this paper, we investigate approximations of the k− th partial ternary cubic derivations on
non-Archimedean ℓ-fuzzy Banach ternary algebras and non-Archimedean ℓ-fuzzy C …

‎ In this paper‎,‎ for a singular perturbation problem consist of the Cauchy-Euler equation with
local and non-local boundary conditions‎.‎ We investigate the condition of the self-adjoint and …