# Is it possible to factor y= x^4 -3x^2 -4 ? If so, what are the factors?

Yes. $x = \pm 2$ or $x = \pm i$
First represent the equation as a quadratic by substituting $z = {x}^{2}$
Then $y = {z}^{2} - 3 z - 4$
This can be factored as $y = \left(z - 4\right) \left(z + 1\right)$
Therefore $z = 4$ or $z = - 1$
Given $z = {x}^{2}$ this means that $x = \pm 2$ or $x = \pm \sqrt{- 1} = \pm i$