已知函数,,若成立,则的最小值是( )A. B. C. D. 答案:【答案】C【解析】令,得到的式子,进而利用导数研究单调性即可得出结果.解:令,则,,解得,,于是,令,则,其中和在上单调递增,且,所以当时,,当时,,故函数在区间上单调递减,在区间上单调递增,所以.即的最小值是.故选:C.1 What does the woman think of the man?
A. He’s serious. B.
He’s honest. C.
He’s humorous.
2 What does the man think of Bob Branson?
A. He has something in
common with the woman.
B. He has nothing in common
with the woman.
C. He’s a good man.