Markdown does not have a way to write math equations.
Recommended solution is to use a web link to a site service which provides math equation view.
Option 1: codecogs website includes an online equation editor which allows generating a link to the equation, like the example bellow.
Option 2: sciweavers website generates a high resolution image from the equation editor.
The website also generates a pure ASCII text version of the equation, ready to include in source code comments
_
/ b
O x
_/ a
-------------------
___________
/ n
3 / partial f
| / ----------
| / n
|/ partial x