Approximate perfect differential equations of second order

Abstract

In this paper we prove the Hyers-Ulam stability of the perfect linear differential equation f(t)y ''(t) + f(1)(t)y'(t) + f(2)(t)y(t) = Q(t), where f, y is an element of C-2[a, b], Q is an element of C[a, b], f(2)(t) = f(1)'(t) - f ''(t) and -infinity < a < b < + infinity.