Đáp án:
$\begin{array}{l}
B1)\\
1)Dkxd:x \ge - 5\\
\sqrt {4x + 20} - 3\sqrt {5 + x} + \dfrac{4}{3}.\sqrt {9x + 45} = 6\\
\Leftrightarrow 2\sqrt {5 + x} - 3\sqrt {5 + x} + \dfrac{4}{3}.3\sqrt {5 + x} = 6\\
\Leftrightarrow 2\sqrt {5 + x} - 3\sqrt {5 + x} + 4\sqrt {5 + x} = 6\\
\Leftrightarrow 3\sqrt {5 + x} = 6\\
\Leftrightarrow \sqrt {5 + x} = 2\\
\Leftrightarrow 5 + x = 4\\
\Leftrightarrow x = - 1\left( {tmdk} \right)\\
Vậy\,x = - 1\\
2)\sqrt {{{\left( {3 - x} \right)}^2}} = 9\\
\Leftrightarrow \left| {3 - x} \right| = 9\\
\Leftrightarrow \left[ \begin{array}{l}
3 - x = 9\\
3 - x = - 9
\end{array} \right.\\
\Leftrightarrow \left[ \begin{array}{l}
x = - 6\\
x = 12
\end{array} \right.\\
Vậy\,x = - 6;x = 12\\
3)Dkxd:x \ge 2\\
\sqrt {9\left( {x - 2} \right)} = 15\\
\Leftrightarrow 9\left( {x - 2} \right) = 225\\
\Leftrightarrow x - 2 = 25\\
\Leftrightarrow x = 27\left( {tmdk} \right)\\
Vậy\,x = 27\\
4)\sqrt {{x^2} - 6x + 9} - 2 = 3\\
\Leftrightarrow \sqrt {{{\left( {x - 3} \right)}^2}} = 5\\
\Leftrightarrow \left| {x - 3} \right| = 5\\
\Leftrightarrow \left[ \begin{array}{l}
x - 3 = 5\\
x - 3 = - 5
\end{array} \right.\\
\Leftrightarrow \left[ \begin{array}{l}
x = 8\\
x = - 2
\end{array} \right.\\
Vậy\,x = 8;x = - 2\\
B2)1)\sqrt {32} + \sqrt {50} - 2\sqrt 8 + \sqrt {18} \\
= 4\sqrt 2 + 5\sqrt 2 - 2.2\sqrt 2 + 3\sqrt 2 \\
= 8\sqrt 2 \\
2)\dfrac{3}{{\sqrt 2 - 2}} - \dfrac{{\sqrt 6 + \sqrt 2 }}{{\sqrt 3 + 1}} - 2\sqrt 2 \\
= \dfrac{{3\left( {\sqrt 2 + 2} \right)}}{{2 - 4}} - \dfrac{{\sqrt 2 \left( {\sqrt 3 + 1} \right)}}{{\sqrt 3 + 1}} - 2\sqrt 2 \\
= \dfrac{{ - 3\sqrt 2 - 6}}{2} - \sqrt 2 - 2\sqrt 2 \\
= - \dfrac{{9\sqrt 2 }}{2} - 3\\
3)\sqrt {96} - 6\sqrt {\dfrac{2}{3}} + \dfrac{3}{{3 + \sqrt 6 }} - \sqrt {10 - 4\sqrt 3 } \\
= 4\sqrt 6 - 6.\dfrac{{\sqrt 6 }}{3} + \dfrac{{3\left( {3 - \sqrt 6 } \right)}}{{9 - 6}} - \sqrt {10 - 4\sqrt 3 } \\
= 4\sqrt 6 - 2\sqrt 6 + 3 - \sqrt 6 - \sqrt {10 - 4\sqrt 3 } \\
= \sqrt 6 + 3 - \sqrt {10 - 4\sqrt 3 } \\
4)2\sqrt {80} + \sqrt {{{\left( {\sqrt 5 - 3} \right)}^2}} - 35\sqrt {\dfrac{1}{5}} \\
= 2.4\sqrt 5 + 3 - \sqrt 5 - 7\sqrt 5 \\
= 3
\end{array}$
