Question

Which polynomial equations have -i as one of their roots?

Answer 1

I = sqrt(-1)
i^2 = -1
(-i)^2 = (-i)(-i) = i^2 = -1
(-i)^3 = (-i)(-i)(-i) = (-i)(i^2) = i

use these facts to find which equation is correct if x = -i

i bet on 2,3 or 4