2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/126525In this paper, we consider the second-order equations of Duffing type. Bounds for the derivative of the restoring force are given that ensure the existence and uniqueness of a periodic solution. Furthermore, the stability of the unique periodic solution is analyzed; the sharp rate of exponential decay is determined for a solution that is near to the unique periodic solution.Key words: Periodic solution; Stability; Rate of decayClassical Analysis and ODEs34B15; 34D05text