Nearly Radical Quadratic Functional Equations in p-2-Normed Spaces

Abstract

We establish some stability results in 2-normed spaces for the radical quadratic functional equation 𝑓(∑𝑛𝑖=1(𝑥𝑖+𝑦𝑖)2)+𝑓(∑𝑛𝑖=1(𝑥𝑖−𝑦𝑖)2)=2∑𝑛𝑖=1(𝑓(𝑥𝑖)+𝑓(𝑦𝑖)) and then use subadditive functions to prove its stability in 𝑝-2-normed spaces.