名校
解题方法
1 . “切线放缩”是处理不等式问题的一种技巧. 如:
在点
处的切线为
,如图所示,易知除切点
外,
图象上其余所有的点均在
的上方,故有
. 该结论可通过构造函数
并求其最小值来证明. 显然,我们选择的切点不同,所得的不等式也不同. 请根据以上材料,判断下列命题中正确命题的个数是( )
;
②
;
③
;
④
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/12a3fe2ef17248ee89e1ca43c0db267a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/807d5f1676dc00e9b0af4656ce047170.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5ab466aedd6e176088d8dee7bc3e3aaa.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/807d5f1676dc00e9b0af4656ce047170.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/12a3fe2ef17248ee89e1ca43c0db267a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5ab466aedd6e176088d8dee7bc3e3aaa.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/92b3a5e0854a552973617a73ca89a6c1.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/10a4c61536e3e24b760066c88d5762a8.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ff62be512f2e053659ed6e355adc3cc0.png)
②
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e121b3db6729caa8fade2d606c5abd69.png)
③
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c72f9fe9af333736b87aaeb5e331d5e5.png)
④
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2a0895395eb64cb1d82cb01eedc75820.png)
A.![]() | B.![]() | C.![]() | D.![]() |
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