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解题方法
1 . 函数极限是现代数学中非常重要的概念,函数
在
处的极限定义如下:
,存在正数
,当
时,均有
,则称
在
处的极限为A,记为
,例如:
在
处的极限为2,理由是:
,存在正数
,当
时,均有
,所以
.已知函数
,
,(
,
为自然对数的底数).
(1)证明:
在
处的极限为
;
(2)若
,
,
,求
的最大值;
(3)若
,用函数极限的定义证明:
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/09f86f37ec8e15846bd731ab4fcdbacd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/11abb76da45ffa52b47c3a6b9a03ac7e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b4c9705e4d8649224c47228f0d1d0f2e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/700458c01a7ad031e27d80ed43e9e882.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/09806564a0244b420341e5366f136f58.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/761be12e359f89c7627eb9200ba0912b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/09f86f37ec8e15846bd731ab4fcdbacd.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/11abb76da45ffa52b47c3a6b9a03ac7e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8abb00b0020eb89f4d18d1a5903f8a32.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2d3cc66b811ad2395efe04d93b61c711.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/9b384412acba251d87902ab928902f16.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b4c9705e4d8649224c47228f0d1d0f2e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/08c75767ddbba7462a85c9061334f3ee.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/93b55b95a7e906eeab34824633ddcae4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c905859cee13de51b09fa4ed56bcfb25.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/a67a4f8bfae051fca5537eca72aff172.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/1381493282b0864315ac49f14eeca20d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c94f94e5acf49264b65ad8bc4b92d316.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/94440d3e4c073f94f2b266ff99d50e74.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/041a7c8fc017f596542c5e6ec7d1c40b.png)
(1)证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4669810732b633b60dbeaf0bf57204f6.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/187c21027ff08411931d32c530b64fd3.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6bd1d338bd463d522aafd98357c4c012.png)
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/57a9bb26472ca40b8a619bfd9ea06a9b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/2492d486aef92677bc4d9c88c28b6845.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/26d8dafc71b106f39f4e15442220897b.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/90132e65026968c74776c719242ecd0c.png)
(3)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/86b85c1784366cf7f60aa01dd62e529d.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8c58fea3170ce3e4fabed81babd54de1.png)
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