Oscillation of second order delay differential equations

摘要

We establish the oscillation criteria for the second order functional equationx(t)+∑i=1lci(t)x(t-τi)″+∑i=1mpi(t)x(t-δi)-∑i=1nqi(t)x(t-σi)=0andx(t)+∑i=1lci(t)x(t-τi)″+∑i=1mpi(t)x(t-δi)-∑i=1nqi(t)x(t-σi)=f(t).New oscillation criteria improve the one recently established by Manojlovic et al. [J. Manojlovic, Y. Shoukaku, T. Tanigawa, N. Yoshida, Oscillation criteria for second order differential equations with positive and negative coefficients, Appl. Math. Comp. 181 (2006) 853–863].