Abstract
The Hyers-Ulam stability, the Hyers-Ulam-Rassias stability, and
also the stability in the spirit of Gavruţa for each of
the following quadratic functional equations
The Hyers-Ulam stability, the Hyers-Ulam-Rassias stability, and
also the stability in the spirit of Gavruţa for each of
the following quadratic functional equations