To write Mathematical Expression on the site or comment box, enclosed your expression between tag [pmath size=xx] …expression.. [/pmath], where xx denotes font size (an integer value).

For example: to display (a+b)^2=a^2+2ab+b^2,

use, [pmath size=xx] (a+b)^2=a^2+2ab+b^2 [/pmath]

For more details refer to Details