等价无穷小

![image1](/img/user/resources/attachments/image1-16 3.png)![image2](/img/user/resources/attachments/image2-13 3.png)

这里用到 x~ln(x+1) 这个等价无穷小，洛必达就会十分复杂
![image3](/img/user/resources/attachments/image3-8 2.png)