Possible Duplicate:
Applying difference of cubes to cube roots
I am a little confused with this question, as I am trying to rationalize the denominator, I realize that I would want to use the sum of cubes formula.
$ (x^3+y^3)= (x+y)(x^2-xy+y^2) $
The question being,
$ \frac{1}{\sqrt[3] x + \sqrt[3] y} $
When I apply the above sum of cubes formula, knowing that I have $ (x + y) $ portion already there as $ \sqrt[3] x + \sqrt[3] y $, my denominator still does not rationalize.
What is the best method for rationalizing this denominator?