| $$ \begin{aligned}\sqrt{108}\cdot3& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}18\sqrt{3}\end{aligned} $$ | |
| ① | $$ 3 \sqrt{108} =
3 \sqrt{ 6 ^2 \cdot 3 } =
3 \sqrt{ 6 ^2 } \, \sqrt{ 3 } =
3 \cdot 6 \sqrt{ 3 } =
18 \sqrt{ 3 } $$ |