摘要

In this paper, we concert with the existence of positive solution for the following nonlinear singular differential system with four-point boundary conditions {-x '' = f(t, y), -y '' = g(t, x), ax(0) - beta x'(0) = delta x(1) + gamma x'(1) = 0, y(0) = ay(xi(1)), y(1) = by(xi(2)), where 0 < xi(1) < xi(2) < 1, alpha, beta, delta, gamma, a, b are nonnegative constants such that rho = beta gamma + alpha gamma + alpha delta > 0. By structuring upper and lower solution and using Schauder fixed point theorem, a necessary and sufficient condition for the existence of positive solutions is established. An example is worked out to illustrate our main result.