You must be in the same class as "bordas".
Here is what I said in his post:
I assume you are using the equation:
Theta is the angle Arctan (y/x) where y is the imaginary part and x is the real part of the inner expression (x + iy)^(1/n)
n is the root, like if you want 3rd root n is 3, and r is the magnitude of the inner expression = (x^2 + y^2) ^ (1/2)
plug in each of k = 0, 1, 2
and see what happens.
Also, dont forget De Moivre's formula to solve #2:
z^n = r^n * ( cos (n*T) + i sin (n*T) )
where T is theta, given by the arctan, and r is the magnitude, the same things as above.