9. (16 points) Find the integer part of $\sqrt{100+\sqrt{101+\cdots+\sqrt{999}}}$.

Translate the above text into English, please retain the original text's line breaks and format, and output the translation result directly.
Sure, here is the translated text:

```
9. Let $x_{1}=\sqrt{1000-1}$,
$$
x_{k}=\sqrt{1000-k+x_{k-1}}(k>1) \text {. }
$$

Thus, the original problem is to find the value of $\left[x_{900}\right]$.
Given $x_{1}\sqrt{100}=10$, therefore,
$\left[x_{900}\right]=10$.
```