To use on this blog, you first use a dollar sign and “latex” like this:

$latex x = \frac{ - b \pm \sqrt{b^2 - 4 a c} }{2 a}

then you can close it with another dollar sign:

$.

Putting it all together, the renderer will give you:

Basically, it’s like writing latex, except that every time you have to go into math mode, you have to type “latex” right after the first dollar sign.