Answer
$$\frac{21}{\sqrt{3}}=7\sqrt{3}$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}\frac{21}{\sqrt{3}}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}} \frac{ 21 }{\sqrt{ 3 }} \times \frac{ \color{orangered}{\sqrt{ 3 }} }{ \color{orangered}{\sqrt{ 3 }}} \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}\frac{21\sqrt{3}}{3} \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle3}{\textcircled {3}} } }}} \frac{ 21 \sqrt{ 3 } : \color{blue}{ 3 } }{ 3 : \color{blue}{ 3 } } \xlongequal{ } \\[1 em] & \xlongequal{ }\frac{7\sqrt{3}}{1} \xlongequal{ } \\[1 em] & \xlongequal{ }7\sqrt{3}\end{aligned} $$ | |
| ① | Multiply both top and bottom by $ \color{orangered}{ \sqrt{ 3 }}$. |
| ② | In denominator we have $ \sqrt{ 3 } \cdot \sqrt{ 3 } = 3 $. |
| ③ | Divide both the top and bottom numbers by $ \color{blue}{ 3 }$. |
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