题目

已知F1、F2是双曲线=1的焦点,PQ是过焦点F1的弦,那么|PF2|+|QF2|-|PQ|的值是_____________________. 答案：思路分析：∵双曲线方程为=1,∴2a=8.由双曲线的定义得|PF2|-|PF1|=2a=8               ①|QF2|-|QF1|=2a=8                               ②①+②,得|PF2|+|QF2|-(|PF1|+|QF1|)=16.∴|PF2|+|QF2|-|PQ|=16.答案:16The teachers in the small village his friends to him, so he them very much.A. like; is like B. are like; likes C. is like; likes D. likes; are like