Answer:
1. If you're taking square roots, the number must be a perfect square to give a rational root.
64 = 8^2, so √64 = 8 is rational
Similarly, since
64 = 4^3, ∛64 = 4 is rational.
For small numbers, it's easy to check for possible roots, as there aren't that many candidates. In general, it's much more difficult.
2.
Explanation: