Question

how can I solve w^3=1 if I know that w=z1/a (z^2+az+a^2=0 with z1 the solution of this equasion )

Answer 1

First write it as

w^3 - 1 = 0

Then you can factor using a difference of two cubes (or use division), and solve the quadratic. I can't really tell what you've posted, but this will work.