If Z ^ 3 = 1, then Z ^ 3 + 2Z ^ 2 + 2Z + 20 =?

If Z ^ 3 = 1, then Z ^ 3 + 2Z ^ 2 + 2Z + 20 =?

For the first time, I saw that there is no imaginary unit I in the plural problem. Do you have the wrong number, Z ^ 3 = 1 (1 is I)
If so, from I ^ 2 = - 1, we get z = - I, then the original formula = 18-i