Đáp án:
$\begin{array}{l}
a)2\sqrt {12} + \sqrt {18} - \sqrt {32} \\
= 2.2\sqrt 3 + 3\sqrt 2 - 4\sqrt 2 \\
= 4\sqrt 3 - \sqrt 2 \\
b)\left( {\sqrt {20} - 2\sqrt {45} + \sqrt 5 } \right).\sqrt 5 \\
= \left( {2\sqrt 5 - 2.3\sqrt 5 + \sqrt 5 } \right).\sqrt 5 \\
= \left( { - 3\sqrt 5 } \right).\sqrt 5 \\
= - 3.5\\
= - 15\\
c)\dfrac{2}{{\sqrt {10} - 3}} + \dfrac{2}{{\sqrt {10} + 3}}\\
= \dfrac{{2\left( {\sqrt {10} + 3} \right) + 2\left( {\sqrt {10} - 3} \right)}}{{\left( {\sqrt {10} - 3} \right)\left( {\sqrt {10} + 3} \right)}}\\
= \dfrac{{2\sqrt {10} + 6 + 2\sqrt {10} - 6}}{{10 - 9}}\\
= 4\sqrt {10} \\
d)\sqrt {20} .\sqrt 5 - \sqrt {144} \\
= \sqrt {100} - 12\\
= 10 - 12\\
= - 2
\end{array}$
