题目
题型:解答题难度:简单来源:不详
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042914-64918.png)
(1)若曲线
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042914-59306.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042915-44659.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042915-25013.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042915-44907.png)
(2)求函数
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042915-71453.png)
(3)设函数
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042915-71453.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042915-21781.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042915-34743.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042916-96686.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042916-89223.png)
答案
(2)当
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042916-31715.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042916-39525.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042915-71453.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042917-14652.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042915-71453.png)
当
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042917-14758.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042917-33822.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042917-79383.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042915-71453.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042917-57853.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042915-71453.png)
(3)根据由(2)知
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042915-71453.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042918-55843.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042918-65863.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042918-55843.png)
解析
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042918-75956.png)
∵曲线
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042914-59306.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042915-44659.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042915-25013.png)
∴
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042918-49946.png)
(2)∵
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042918-40588.png)
当
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042916-31715.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042916-39525.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042915-71453.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042917-14652.png)
此时函数
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042915-71453.png)
当
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042917-14758.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042917-33822.png)
当
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042919-60076.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042916-39525.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042915-71453.png)
当
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042919-99631.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042919-84683.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042915-71453.png)
当
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042919-86897.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042916-39525.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042915-71453.png)
∴此时
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042917-79383.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042915-71453.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042917-57853.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042915-71453.png)
(3)不妨设
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042919-42100.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042915-34743.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042915-71453.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042918-55843.png)
又
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042918-65863.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042918-55843.png)
所以要证
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042920-85435.png)
只需证
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042920-84198.png)
设
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042920-19508.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042920-79906.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042920-49116.png)
当
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042921-68815.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042921-24566.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042920-19508.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042918-55843.png)
所以
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042920-84198.png)
所以对任意
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042916-96686.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042920-85435.png)
点评:主要是考查了导数研究函数单调性的运用,以及证明不等式,属于难度题。
核心考点
举一反三
A.![]() | B.![]() |
C.![]() | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042906-20709.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042906-26598.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042906-49602.png)
A.![]() | B.![]() | C.![]() | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042902-57842.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042903-13037.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042903-97861.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042900-71291.png)
A.![]() | B.![]() | C.![]() | D.![]() |
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042858-36377.png)
![](http://img.shitiku.com.cn/uploads/allimg/20190818/20190818042858-99900.png)
A.1 | B.2 | C.![]() | D.0 |
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