Existence of oscillatory solutions of difference equations with positive and negative coefficients (Q2858071)

This paper deals with two oscillation criteria for bounded solutions of the second-order neutral delay difference equation NEWLINE\[NEWLINE \Delta^2(x_n+c_n\,x_{n-k})+p_n\,f(x_{n-l})-q_n\,f(x_{n-m})=0, NEWLINE\]NEWLINE where \(n\geq n_0\in{\mathbb N}\), \(k,l,m\in{\mathbb N}\cup\{0\}\), \(f:{\mathbb R}\to{\mathbb R}\) is continuous with \(f(u)/u\geq\beta>0\) for \(u\neq0\).