Tap the blue circles to see an explanation.
| $$ \begin{aligned}\sqrt{21}+10\sqrt{84}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}\sqrt{21}+20\sqrt{21} \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}21\sqrt{21}\end{aligned} $$ | |
| ① | $$ 10 \sqrt{84} =
10 \sqrt{ 2 ^2 \cdot 21 } =
10 \sqrt{ 2 ^2 } \, \sqrt{ 21 } =
10 \cdot 2 \sqrt{ 21 } =
20 \sqrt{ 21 } $$ |
| ② | Combine like terms |