| $$ \begin{aligned}4\sqrt{10}(-3\sqrt{2})& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-24\sqrt{5}\end{aligned} $$ | |
| ① | $$ - 12 \sqrt{20} =
-12 \sqrt{ 2 ^2 \cdot 5 } =
-12 \sqrt{ 2 ^2 } \, \sqrt{ 5 } =
-12 \cdot 2 \sqrt{ 5 } =
-24 \sqrt{ 5 } $$ |