How to display math equations?

[keybatman]

I typed the Stirling's approximation in LaTeX: $n! \approx \sqrt(2 \pi) n^{n+0.5} / \e^{n}$.
But the readable math equation was not displayed in my blog.
How to fix this please?

btw, the very short equations, eg, $n$ works fine.

[sezan92]

hello , could you solve this issue?