中文摘要：

本文给出方程xn＋1=-xnxn-1/axn＋bxn-2的奇点集，并讨论该方程解的全局行为．我们证明了收敛解要么是一个4周期解，要么收敛到一个4周期解或固定值而不收敛解在一定条件下是无界的．

英文摘要：

In this paper, we discuss the global behavior of a rational difference equation xn＋1=-xnxn-1/axn＋bxn-2We show that for all initial values out side the forbidden set,its convergence solution is ei-ther a 4 periodic solution, or converges to a 4 periodic solution or a fixed value;the non-convergence solu- tion is unbounded under some conditions.