Đáp án:
$\begin{array}{l}
\sqrt {72} + \sqrt {4\dfrac{1}{2}} - \sqrt {32} - \sqrt {162} \\
= \sqrt {36.2} + \sqrt {\dfrac{9}{2}} + \sqrt {16.2} + \sqrt {81.2} \\
= \sqrt {36} .\sqrt 2 + \sqrt 9 .\sqrt {\dfrac{1}{2}} + \sqrt {16} .\sqrt 2 + \sqrt {81} .\sqrt 2 \\
= 6\sqrt 2 + 3.\dfrac{{\sqrt 2 }}{2} + 4\sqrt 2 + 9\sqrt 2 \\
= \left( {6 + \dfrac{3}{2} + 4 + 9} \right).\sqrt 2 \\
= \dfrac{{41\sqrt 2 }}{2}
\end{array}$
