Question 251257
1. (-x-^2 y^3) /(5y-^2)^2 

{{{-x^-2y^3}}} / {{{(5y^-2)^2}}}

square the denominator . . .

{{{-x^-2y^3}}} / {{{25y^-4}}}

rewrite using positive exponents . . .

{{{-y^7}}} / {{{25x^2}}}

2. (a-^2/3 b^3/4) (a^1/4 b^2/3)

{{{a^(-2/3)b^(3/4)}}} * {{{a^(1/4)*b^(2/3)}}}

When you multiply the bases add the exponents . . . 

{{{a^(-5/12)b^(17/12)}}}

rewrite using positive exponents . . . 

{{{b^(17/12) / a^(5/12)}}} or b^(17/12) / a^(5/12)