... & Sons, New York, NY, USA,Science edition, 1940.2 D. H. Hyers, On the stability of the linear functional equation,” Proceedings of the National Academy of Sciences of the United States of ... 8–13.One should remember that the functional equation is called stable if any approximately solution to the functional equation is near to a true solution of that functional equation, and ... quadratic functional equation. In addition, every solution of functional eqaution1.6 is said to be a quadratic mapping. A Hyers-Ulam stability problem for the quadraticfunctional equation was proved...