I am looking through the text book to find how you came to the conclusion to use a square of a difference in this case. the radical is cubed so I would thought to use differences of two cubes?
Or am I confused with the radicals somehow? If I disregard manipulating the numerator and just assume the difference of two cubes will remove the radicals my answer is correct. But I am missing something seriously with my understanding of polynomial manipulation because when I actually do the calculation. I get the result below which shows that something is not correct.
Please can you explain exactly why you came to this conlusion?
I am trying to understand what to look for to solve the problem myself but getting the answer still does not explain the process it takes to reach the conclusion.