LaTex grammer

[Link](https://math.meta.stackexchange.com/questions/5020/mathjax-basic-tutorial-and-quick-reference)
link url:
>https://math.meta.stackexchange.com/questions/5020/mathjax-basic-tutorial-and-quick-reference

for ex.
```
 - in the line: $\Gamma(n) = (n-1)!\quad\forall n\in\mathbb N$。
 - block:
 
$$	x = \dfrac{-b \pm \sqrt{b^2 - 4ac}}{2a} $$
```

 - in the line: $\Gamma(n) = (n-1)!\quad\forall n\in\mathbb N$。
 - block:
 
$$	x = \dfrac{-b \pm \sqrt{b^2 - 4ac}}{2a} $$