First, you would square everything inside the parenthesis and you would get:
9(a^-4)(b^2)/(a^2)(b^-3)
Then, you would put the variables with negative exponents onto the opposite side, so that all the exponents are positive.
9(b^3)(b^2)/(a^2)(a^4)
Then you would add like terms and end up with:
9(b^5)/(a^6)
