题目

若，且．
（1）求的最小值及对应的x值；
（2）若不等式的解集记为A，不等式的解集记为B，求．

答案

20．(1) ∵
∴，∴
∴a = 2或a = 1（舍）····································································· 2分
又∵
∴ ∴b=" 2······························································" 4分
∴，
∴当时，的最小值为······························· 6分
(2) 由
∴
∴
∴，即······································· 9分
由
∴
∴······································································· 11分
∴···································································· 12分

解析

略