Question 172081
Hint 1:  {{{a-b=-(b-a)}}} so {{{1-9y=-(9y-1)}}}


Hint 2:  {{{a^2-b^2=(a+b)(a-b)}}} so {{{y^2-81=(y+9)(y-9)}}}


Hint 3:  To divide one fraction by the other, invert the divisor and multiply.