Question

Given z = 2 - j2 is the root of
2z^3 – 9z^2 +20z – 8 = 0
find the remaining roots of the equation.

Answer 1

Since the conjugate is another root, we have z=2+j2, which means that
(z+2+j2)(z+2-j2)=(z^2+4z+8) is a factor.
The remaining factor can be deduced by synthetic division (2z-1), or z=1/2.