(x^-3+y^-1)/x^-2

Note that

x^-2 = 1/x^2
Therefore,
(x^-3 + y^-1) / x^-2
= (1/x^3 + 1/y) / 1/x^2
= (x^2)(1/x^3 + 1/y)
= (x^2 / x^3) + (x^2 / y)
= 1/x + x^2/y