POSITIVE PERIODIC SOLUTIONS OF NONLINEAR DIFFERENTIAL EQUATIONS

摘要

The nonlinear differential equation x′(t) = - δ(t) x (t) + f(t,x(t)) (*) is considered, where δ(t) is a periodic function of periodic T, f(t, x) is continuous and periodic in t. It is showed that ( * ) has at least two positive T-periodic solutions under certain growth conditions imposed on f. Applications will be presented to illustrate the main results.