| $$ \begin{aligned}\sqrt{15}\cdot(6+\sqrt{2})& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}6\sqrt{15}+\sqrt{30}\end{aligned} $$ | |
| ① | $$ \color{blue}{ \sqrt{15} } \cdot \left( 6 + \sqrt{2}\right) = \color{blue}{ \sqrt{15}} \cdot6+\color{blue}{ \sqrt{15}} \cdot \sqrt{2} = \\ = 6 \sqrt{15} + \sqrt{30} $$ |