Real image the complex polynomial Find $z \in \mathbb{C}$ such that $p(z)=z^4-6z^2+25<0$
I think that the solution for this problem is the following: 
$$p(z)=z^4-6z^2+25=(z^2-3)^2+16$$
Thus, 
$$p(z)<0 \Leftrightarrow (z^2-3)^2+16<0 \Leftrightarrow (z^2-3)^2<-16$$
But, I see not how find $z$.

$$z^2-3=4ki$$,any $$|k|>1,z=\sqrt{(3-4ki)}$$.
