c: \(\dfrac{-2x^4y^3}{6xy}=\dfrac{-2xy\cdot x^3y^2}{2xy\cdot3}=\dfrac{-x^3y^2}{3}=\dfrac{-x^3y^2\cdot x^2y^2}{3x^2y^2}=\dfrac{-x^5y^4}{3x^2y^2}\)
d:
\(\dfrac{x^3-y^3}{2x^2y-2xy^2}\)
\(=\dfrac{\left(x-y\right)\left(x^2+xy+y^2\right)}{2xy\left(x-y\right)}\)
\(=\dfrac{x^2+xy+y^2}{2xy}\)