To use 
$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.
Now, if only wordpress can make it so the images have a transparent background instead of a white background. They use PNGs for the images, so there really is no excuse on their part.
Yeah, it looks pretty atrocious in RSS readers without a white background. I had some problems with transparency in PNGs due to cross-platform issues (creating the transparency on a Mac wouldn’t read in Windows), so maybe they’re “playing it safe?” That was a few years ago, though….
wow, it works 😀