选修4—5;不等式选讲 已知对于任意非零实数,不等式恒成立,求实数的取值范围. 答案:解:即恒成立 (2分) 只需 (1)当时,原式,即 (5分) (2)当时,原式,即 (7分) (3)当时,原式,即 (9分) 综上的取值范围为 (10分)根据以下要点,以“My hometown” 为题写一篇80词左右的短文。 Dongtai In the pastAt present Environmentnarrow and dirty roads, rubbish everywhere, large open spaceswide and clean streets , green trees on both sides , shops and tall buildings Lifesmall old houses , listen to the radio or watch TV new flats , computers and the Internet , mobile phones Transporton foot or by bicycleby bus or taxi , have own cars Opinion enjoy a comfortable life My hometown________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________