BHAVIN MANSUKHLAL PATEL. On the Stability of the Quadratic Functional Equation $f(2x+y) + f(x+2y)$ $= 4f(x+y) + f(x) + f(y)$ in $2$-Banach Space. International Journal of Mathematics And its Applications, [S. l.], v. 13, n. 4, p. 41–53, 2026. Disponível em: https://ijmaa.in/index.php/ijmaa/article/view/1631. Acesso em: 9 jan. 2026.