How would you simplify this?
$\displaystyle (a-b)^2(a+b)2$
if you meant ...
$\displaystyle (a-b)^2(a+b)^2$ ...
$\displaystyle (a-b)(a-b)(a+b)(a+b)
$
$\displaystyle (a-b)(a+b)(a-b)(a+b)$
$\displaystyle (a^2-b^2)(a^2-b^2)$
$\displaystyle (a^2-b^2)^2$
btw, I do not consider this to be "simplification" ... just changing the expression's looks.