This Firefox/IE plugin allows you to solve and simplify mathematical expressions right from your search bar.

This plugin is a work-in-progress, and may not solve and/simplify everything.
However, it is supposed to handle: reduction of constants, removal of unneeded parentheses, reduction of similar factors and terms, linear equations, quadratics, some polynomial reductions, associative property, and some substitutions.
Use * to multiply, ^ for exponentiation, and / to divide.
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This math hack only works if one of your numbers is even, but it’s a quick way to manipulate numbers to get the answer you need quick.