Find the domain (of a function to the third degree)?

Question

Find the domain:

1) 1 / (x^3 + 25)

2) 1 / (x^3 - 25)

Answer 1

in both questions you need the denominator to be different from 0
so
1) x^3 + 25 =0
x=-cube root 25
2) x^3 -25 =0
x = cube root 25

Answer 2

1) all real # but not (-25)^(1/3)
2) all real # but not (25)^(1/3)

it can never be #/zero