Explanation:
The following is a list of perfect Cubes
13 = 1
23 = 8
33 = 27
43 = 64
53 = 125
63 = 216
73 = 343
83 = 512
93 = 729
103 = 1000
If a variable with an exponent has an exponent which is divisible by 3 then it is a perfect cube. To get the cube root, we simply divide the exponent by 3. For example x9 is a perfect cube, its cube root is x3 . x11 is not a perfect cube.