Multiple periodic solutions of differential delay equations x'(t)=-+ sum _(i=1)~(n-1) delta_if (x(t-r_i)) with delta_i = +-1

摘要

This paper is a further extension of our recent work (3-6). We shall generally study the existence of multiple periodic solutions of differential delay equations x'(t)=-+sum from i=1 to n-1 delta_if(x(t-r_i)), (1.1)_(+-) where delta_1 ident to 1, delta_i = 1 or -1 for i = 2, -, n-1, r_i>0 for i = 1, -, n-1.