Simplify: x−2y3x−4y−1\frac{x^{-2}y^3}{x^{-4}y^{-1}}x−4y−1x−2y3
x2y4\frac{x^2}{y^4}y4x2
x2y4x^2y^4x2y4
y4x2\frac{y^4}{x^2}x2y4
x6y2\frac{x^6}{y^2}y2x6