On the solution and stability of the quadratic type functional equations

Commun. Korean Math. Soc. 2004 Vol. 19, No. 3, 477-493 Printed September 1, 2004

Eun Hwi Lee Jeonju University

Abstract : In this paper we prove the solution and stability of the quadratic type functional equations with two variables $$4f(\frac{x-2y}{2})+f(x)+2f(y)=8f(\frac{x-y}{2})+f(2y)$$ and $$ f(x-2y) + f(x)+2f(y)=2f(x-y)+f(2y).$$