$$ \begin{aligned}5\sqrt{441}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}5\cdot21 \xlongequal{ } \\[1 em] & \xlongequal{ }105\end{aligned} $$ | |
① | The square root of $ 441 $ is $ 21 $. |