题目
题型:不详难度:来源:
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053454-59871.png)
(1)判断函数
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053454-95795.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053454-37337.png)
(2)设
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053454-61908.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053454-95795.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053454-12345.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053454-61908.png)
答案
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053455-41120.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053454-95795.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053455-69050.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053454-95795.png)
(2)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053455-62570.png)
解析
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053455-85555.png)
(II)在(I)的基础上,要根据a的取值范围讨论它在[1,2]上的单调性,进而可确定出f(x)在[1,2]上的最大值.注意连续函数在闭区间上的最值问题不在极值处取得就在区间端点处取得.
解:(1)由已知
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053455-85555.png)
注意到
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053455-45598.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053455-99434.png)
解
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053455-75401.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053455-72642.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053455-39974.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053456-12507.png)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053455-41120.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053454-95795.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053455-69050.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053454-95795.png)
(2)由(1)知
当
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053456-73741.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053456-96621.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053454-95795.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053456-58832.png)
当
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053456-20123.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053457-94341.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053454-95795.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053457-49086.png)
当
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053457-19249.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053457-50494.png)
因为
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053457-46387.png)
所以,当
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053458-53605.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053454-95795.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053457-49086.png)
当
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053458-26409.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053454-95795.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053456-58832.png)
综上,
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053458-21084.png)
核心考点
举一反三
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053448-79149.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053448-62106.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053449-14162.png)
A.必要不充分条件 | B.充分不必要条件 |
C.充要条件 | D.既不充分也不必要条件 |
A.若![]() ![]() ![]() |
B.若![]() ![]() ![]() ![]() |
C.函数![]() |
D.定义在![]() ![]() ![]() ![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053434-91671.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053434-25106.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053434-81201.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053434-81201.png)
A.0 | B.![]() | C.0或![]() | D.0或1 |
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053427-14856.png)
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053427-64775.png)
A.![]() | B.![]() | C.![]() | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20191018/20191018053424-30976.png)
A.![]() | B.![]() | C.![]() | D.![]() |
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