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