A FIXED POINT APPROACH TO THE STABILITY OF THE QUADRATIC AND CUBIC TYPE FUNCTIONAL EQUATION

In this paper, I investigate the stability of the functional equation f (x + 2y) − 3f (x + y) + 3f (x) − f (x − y) − 3f (y) + 3f (−y) = 0 by using the fixed point theory in the sense of L. Cādariu and V. Radu.