How do you factor $-x^2y^2 + x^4 + 4y^2 - 4x^2$ ?

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Answer 1 · 2016-02-02T11:27:08

Combination

We have the equation as

$f(x,y) = -x^2y^2+x^4+4y^2-4x^2$
$= x^4-x^2y^2-4x^2+4y^2$
$= x^2(x^2-y^2)-4(x^2-y^2)$
$= (x^2-y^2)\times (x^2-4)$

How do you factor -x^2y^2 + x^4 + 4y^2 - 4x^2 -x^2y^2 + x^4 + 4y^2 - 4x^2 ?