Use the given root to find the solution set of the polynomial equation.

Question

x^3 + 8x^2 -18x +20= 0 ; 1+i

Answer 1

If 1+i is a root, so is 1-i
So, (x-(1+i))(x-(1-i)) divides the cubic polynomial

(x^2-2x+2)(x+10) = 0
so, the roots are 1+i, 1-i, -10