won't evaluate answers given by solve()

edit

I am solving an equation and then trying to plug in the answers it gives to show that the answers are correct, but sage will not evaluate the answers i plug in.

solve(x^3+1==0,x)

yields

[x == 1/2*I*sqrt(3)*(-1)^(1/3) - 1/2*(-1)^(1/3), 
x == -1/2*I*sqrt(3)*(-1)^(1/3) - 1/2*(-1)^(1/3), 
x == (-1)^(1/3)]

if you then put into sage (1/2*I*sqrt(3)*(-1)^(1/3) - 1/2*(-1)^(1/3))^3+1 the result it gives is (1/2*I*sqrt(3)*(-1)^(1/3) - 1/2*(-1)^(1/3))^3 + 1. it's like it doesn't know what to do with it's own answers.