I've always thought that the hardest part of any math problem is understanding the problem itself. You've given us an expression, but there are lots of things that we could do with it. First go back and make sure you understand what the problem is asking you to do.
For example, you may want to know how to expand it so that you can express it as a polynomial. If this is the case a hint would be to do a substitution: Let a1/3 = x and let b1/3 = y. Write your expression in terms of x and y, and see if this helps.