Math
posted by CheezyReezy on .
Find all complex zeros for the following polynomial function. Please show all of your work.
f(x) = x^4  91x^2  900
Hi, I need help... I'm not understanding this complex zero..

Substitute: x^2=z => x^4=z^2
z^291z900=0
(z100)(z+9)=0
If z=100, x^2=100 then x=10 or x=10
If z=9, x^2=9=9i^2 then x=3i or x=3i