im having trouble factoring this completely

[dmaster564]

i cant figure out how to factor this problem completely. it would be nice if someone helped me, i have worked on this for hours 9u^2-9v^2-36w^2+36vw (this is the problem)
i got this far 9(u^2-v^2-4w^2+4vw)

 

[Loren]

Your next step is to rearrange so that you will get a pattern like this.

k(x[sup:1mps7c8w]2[/sup:1mps7c8w] - y[sup:1mps7c8w]2[/sup:1mps7c8w] + 4yz - 4z[sup:1mps7c8w]2[/sup:1mps7c8w])

Then work with it as the difference of two perfect squares, the first being a monomial and the second being a trinomial, a negative 1 being factored out of the trinomial.