$$ \begin{aligned}\sqrt{6}\cdot9\sqrt{12}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}54\sqrt{2}\end{aligned} $$ | |
① | $$ 9 \sqrt{72} =
9 \sqrt{ 6 ^2 \cdot 2 } =
9 \sqrt{ 6 ^2 } \, \sqrt{ 2 } =
9 \cdot 6 \sqrt{ 2 } =
54 \sqrt{ 2 } $$ |