Positive periodic solutions for second-order neutral differential equations with functional delay

Abstract

We use Krasnoselskii’s fixed point theorem to prove the existence of positive periodic solutions of the second-order nonlinear neutral differential equation d2dt2x(t) + p(t)ddtx(t) + q(t)x(t) = cddtx(t − τ(t)) + f(t, h(x(t)), g(x(t − τ(t))))