The first message already shows several examples.
Here is another example:
If you type 
[quote]
the root for $a*x^2+b*x+c=0$ is $x=\frac{-b\pm\sqrt{b^2-4*a*c}}{2*a}$
[/quote]
You will get

the root for a*x^2+b*x+c=0 is x=\frac{-b\pm\sqrt{b^2-4*a*c}}{2*a}