Đáp án:
Giải thích các bước giải:
\(\begin{array}{l}
1)\,\,a)\,\,\sqrt {50} + \sqrt {48} - \sqrt {72} = \sqrt {25.2} \, + \sqrt {16.3} \, - \sqrt {36.2} \\
\,\,\,\,\,\,\,\,\,\,\,\, = 5\sqrt 2 + 4\sqrt 3 - 6\sqrt 2 = 4\sqrt 3 - \sqrt 2 \\
b)\,\,\frac{3}{{\sqrt 2 - 1}} - \frac{3}{{\sqrt 2 + 1}} = \frac{{3\left( {\sqrt 2 + 1} \right) - 3\left( {\sqrt 2 - 1} \right)}}{{\left( {\sqrt 2 - 1} \right)\left( {\sqrt 2 + 1} \right)}}\\
\,\,\,\,\,\,\, = \frac{{3\sqrt 2 + 3 - 3\sqrt 2 + 3}}{{2 - 1}} = 6\\
2)\,\,a)\,\,\sqrt {3 + 2x} = 5\,\,\,\,\, & DK:\,\,x \ge \frac{{ - 2}}{2}\\
\,\,\,\,\,\, \Leftrightarrow 3 + 2x = 25\\
\,\,\,\,\,\, \Leftrightarrow 2x = 22\\
\,\,\,\,\,\, \Leftrightarrow x = 11\,\,(TM)\\
Vay:\,\,x = 11.\\
b)\,\,\,\sqrt {{{(x - 2)}^2}} = 8\\
\Leftrightarrow \left| {x - 2} \right| = 8\\
\Leftrightarrow \left[ \begin{array}{l}
x - 2 = 8\\
x - 2 = - 8
\end{array} \right. \Leftrightarrow \left[ \begin{array}{l}
x = 10\\
x = - 6
\end{array} \right.
\end{array}\)
