Đáp án:
$\begin{array}{l}
a)3\sqrt 8 - 6\sqrt {\dfrac{1}{{18}}} + \dfrac{{\sqrt 2 - 2}}{{\sqrt 2 }}\\
= 3.2.\sqrt 2 - 6.\dfrac{1}{{\sqrt {9.2} }} + \dfrac{{\sqrt 2 \left( {1 - \sqrt 2 } \right)}}{{\sqrt 2 }}\\
= 6\sqrt 2 - 6.\dfrac{{\sqrt 2 }}{{3.2}} + \left( {1 - \sqrt 2 } \right)\\
= 6\sqrt 2 - \sqrt 2 + 1 - \sqrt 2 \\
= 4\sqrt 2 + 1
\end{array}$