Remarks on the stability of Drygas' equation and the Pexider-quadratic equation
The author proves the Hyers-Ulam stability of the Pexider-quadratic equation and Drygas' equation on a class of groups, with sharper bounds. An example is also given to illustrate that the quadratic functional equation is not stable in general on non abelian groups.
scientific article; zbMATH DE number 2113899