I have to determine what kind of function these are and so have i have deteremined what they are NOT

2x^-3 + 5x^-2 +6

2x^2 + t^(1/3)

__GR__

x^3 - 8

I have determined they are all neither polynomial or rational

i believe the 2nd is a power function

how do i tell which is which?? thanks