2.c) on page 56. I’ve tried rationalizing, changing 2/3 into a decimal, u substitution for the function given as well as usubstitution for the term just under the root ie 1/u. All of these have turned out pretty ugly and have not given me the answer of -1/27. How do I approach this question without needing metres of chart paper?

Possible solution...
oh and ive also tried changing the root to an exponent, no luck on that either