In this paper, we prove two general theorems about Hyers-Ulam stability of functional equations. As particular cases we obtain many of the results published in the last ten years on the stability of the Cauchy and quadratic equation.
Brzdek, J., Belluot, N. B., Cieplinski, K., Jung, S. M., & Xu, B. (2013). Ulam\'s Type Stability 2013. Abstract and Applied Analysis, 2013(), 752-753-684. https://doi.org/10.1155/2013/546406