Đáp án:
$\begin{array}{l}
1)3\sqrt 2 - 4\sqrt {18} + 2\sqrt {32} - \sqrt {50} \\
= 3\sqrt 2 - 4.3\sqrt 2 + 2.4\sqrt 2 - 5\sqrt 2 \\
= 3\sqrt 2 - 12\sqrt 2 + 8\sqrt 2 - 5\sqrt 2 \\
= - 6\sqrt 2 \\
2)\sqrt {50} - \sqrt {18} + \sqrt {200} - \sqrt {162} \\
= 5\sqrt 2 - 3\sqrt 2 + 10\sqrt 2 - 9\sqrt 2 \\
= 3\sqrt 2 \\
3)5\sqrt 5 + \sqrt {20} - 3\sqrt {45} \\
= 5\sqrt 5 + 2\sqrt 5 - 3.3\sqrt 5 \\
= - 2\sqrt 5 \\
4)5\sqrt {48} - 4\sqrt {27} - 2\sqrt {75} + \sqrt {108} \\
= 5.4\sqrt 3 - 4.3\sqrt 3 - 2.5\sqrt 3 + 6\sqrt 3 \\
= 20\sqrt 3 - 12\sqrt 3 - 10\sqrt 3 + 6\sqrt 3 \\
= 4\sqrt 3 \\
5)3\sqrt {12} - 4\sqrt {27} + 5\sqrt {48} \\
= 3.2\sqrt 3 - 4.3\sqrt 3 + 5.4\sqrt 3 \\
= 6\sqrt 3 - 12\sqrt 3 + 20\sqrt 3 \\
= 14\sqrt 3 \\
6)\sqrt {12} + 5\sqrt 3 - \sqrt {48} \\
= 2\sqrt 3 + 5\sqrt 3 - 4\sqrt 3 \\
= 3\sqrt 3 \\
7)2\sqrt {32} + 4\sqrt 8 - 5\sqrt {18} \\
= 2.4\sqrt 2 + 4.2\sqrt 2 - 5.3\sqrt 2 \\
= 8\sqrt 2 + 8\sqrt 2 - 15\sqrt 2 \\
= \sqrt 2
\end{array}$
