You may want to review simplifying roots with variables first.

If the radicand has a denominator, we deal with it just as we did
without variables. For example, if you have to simplify
√(2 ⁄ *a*^{2}), this is the
same as
√(1 ⁄ *a*^{2})√2 =
1 ⁄ *a* * √2. In general, when
you're done, there should be no denominator in the radicand.

As before, it works the same way for higher-order roots.