I have only started playing with it, but MathJax seems like a really nice tool to display math in web pages that is typeset using LaTeX syntax. There are a couple of small differences from a normal LaTeX document.
When $a \ne 0$, there are two solutions to $ax^2 + bx + c = 0$ and they are $$x = {-b \pm \sqrt{b^2-4ac} \over 2a}.$$