On the existence of positive periodic solutions for totally nonlinear neutral differential equations of the second-order with functional delay

Abstract

We prove that the totally nonlinear second-order neutral differential equation $\frac{d^2}{dt^2}x(t)+p(t)\frac{d}{dt}x(t)+q(t)h(x(t))$ $=\frac{d}{dt}c(t,x(t-\tau(t)))+f(t,\rho(x(t)),g(x(t-\tau(t))))$ has positive periodic solutions by employing the Krasnoselskii-Burton hybrid fixed point theorem.