You can put this solution on YOUR website! Notice that 4x^4 and 9y^4 are perfect squares.
(2x^2)^2 = 4x^4
(3y^2)^2 = 9y^4
We have the difference of squares:
Then,
Noticing the same fact that 4x^4 and 9y^4 are perfect squares, and that (2*3)*2 = 12, we can say that
So we have