(a căn a+b căn b chia căn a + căn b) nhân (căn a + căn b chia a-b) mũ 2

\[\begin{array}{l}
\frac{{a\sqrt a + b\sqrt b }}{{\sqrt a + \sqrt b }}.{\left( {\frac{{\sqrt a + \sqrt b }}{{a – b}}} \right)^2}\\
= \frac{{\left( {\sqrt a + \sqrt b } \right)\left( {a – \sqrt {ab} + b} \right)}}{{\sqrt a + \sqrt b }}.\frac{{{{\left( {\sqrt a + \sqrt b } \right)}^2}}}{{{{\left( {\sqrt a – \sqrt b } \right)}^2}{{\left( {\sqrt a + \sqrt b } \right)}^2}}}\\
= \frac{{a – \sqrt {ab} + b}}{{{{\left( {\sqrt a – \sqrt b } \right)}^2}}}.
\end{array}\]