Three periodic solutions for a nonlinear first order functional differential equation

摘要

This paper is concerned with the existence of three positive T-periodic solutions of the first order functional differential equations of the formx′(t)=a(t)x(t)-λb(t)f(t,x(h(t))),where a(t),b(t) and τ(t) are positive T-periodic functions, and λ is a positive parameter. Leggett–Williams multiple fixed point theorem has been used to prove our results. Our results extend and improve some results in the literature.