题目

设关于x的不等式(a-2)x2+2(a-2)x-4＜0的解集为R.求a的取值范围. 答案：解：(1)当a-2=0,即a=2时, 原不等式可化简为-4＜0,成立.∴a=2可取.∴x∈R.(2)当a-2≠0,即a≠2时,若保证x∈R,则有-2＜a＜2.综上,-2＜a≤2.() 2. —How was your last vacation to Beijing?       —    A. It's good   B. They are boring.   C. It was interesting.   D. It was far away.