Hi

I need help on the following equation:

1) $\displaystyle z^4+2z^2+4 =0$

$\displaystyle u=z^2$

$\displaystyle u^2+2u+4=0$

use quadratic equation:

i get

$\displaystyle u= \frac{-2 +\sqrt{16}}{4}$

or

$\displaystyle u= \frac{-2 -\sqrt{16}}{4}$

my question is do i simplify this to find the roots or leave it?

P.S