Difference of squares: a2 - b2 =(a + b)(a - b)

Go !

Calculate and simplify:

$(a^2-b^2)(a^2+b^2) =$
$(xy+3)(xy-3)(\frac{x^2y^2+9}{2}) =$

Factorize:

$x^6-y^2 =$ $(x^3+y)(x^3-y) $
$a^3-ab^2 =$