Let $cal{A}$ be a unital Banach algebra. If f : $cal{A}{ ightarrow}cal{A}$ is an approximately quadratic derivation in the sense of Hyers-Ulam-J.M. Rassias, then f : $cal{A}{ ightarrow}cal{A}$ is anexactly quadratic derivation. On the other hands, let $cal{A}$ and $cal{B}$ be Banach algebras.Any approximately generalized homomorphism f : $cal{A}{ ightarrow}cal{B}$ corresponding to Cauchy, Jensen functional equation can be estimated by a generalized homomorphism.