# Math Help - about factoring 4th power trinomials

1. ## about factoring 4th power trinomials

$x^4-12x^2y^2+16y^2$

the ans to this is

$(x^2 - 2 x y - 4 y^2) (x^2 + 2 x y - 4 y^2)$

but I don't what steps are taken to get this I tried U subst
but that did not seem to get this. looks like a plug in type solution
but textbook does not show one

thnx ahead

2. ## Re: about factoring 4th power trinomials

Originally Posted by bigwave
$x^4-12x^2y^2+16y^2$

the ans to this is

$(x^2 - 2 x y - 4 y^2) (x^2 + 2 x y - 4 y^2)$

but I don't what steps are taken to get this I tried U subst
but that did not seem to get this. looks like a plug in type solution
but textbook does not show one

thnx ahead

Suppose that $y=1$, then what happens?

3. ## Re: about factoring 4th power trinomials

well if $y=1$ you get

$(x^2-2 x-4) (x^2+2 x-4)$

but I don't see how you develop to get 2 tri nominals multiplied together from factoring this