Simplify: x−2y3x3y−1\frac{x^{-2} y^3}{x^3 y^{-1}}x3y−1x−2y3 for x,y≠0x, y \neq 0x,y=0.
y4x5\frac{y^4}{x^5}x5y4
y2x\frac{y^2}{x}xy2
x5y4x^5 y^4x5y4
1xy\frac{1}{x y}xy1