| $$ \begin{aligned}\sqrt{7}\cdot(\sqrt{7}+\sqrt{2})& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}7+\sqrt{14}\end{aligned} $$ | |
| ① | $$ \color{blue}{ \sqrt{7} } \cdot \left( \sqrt{7} + \sqrt{2}\right) = \color{blue}{ \sqrt{7}} \cdot \sqrt{7}+\color{blue}{ \sqrt{7}} \cdot \sqrt{2} = \\ = 7 + \sqrt{14} $$ |