how do i do this?

Question

factor x^4-x^2-20 over real and complex numbers

I tried to do synthetic, but it doesnt work.=(

Answer 1

Gedunken.

(x^2-5)(x^2+4)

Now each of those can be factored, the first give real, the second imaginary roots.

Answer 2

WOAH. how did u know how to do that?
like, waht is the rule?

is gedunken a person?