Đáp án:
$\begin{array}{l}
c)\frac{{{x^3}}}{{{x^3} - 3{x^2}y + 3x{y^3} - {y^3}}} = \frac{{{x^3}}}{{{{\left( {x - y} \right)}^3}}} = \frac{{{x^3}.y}}{{y{{\left( {x - y} \right)}^3}}}\\
\frac{x}{{{y^2} - xy}} = \frac{x}{{y\left( {y - x} \right)}} = \frac{{ - x{{\left( {x - y} \right)}^2}}}{{y{{\left( {x - y} \right)}^2}}}
\end{array}$