Question
Answer
$$-3\sqrt{21}+7\sqrt{84}=11\sqrt{21}$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}-3\sqrt{21}+7\sqrt{84}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-3\sqrt{21}+14\sqrt{21} \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}11\sqrt{21}\end{aligned} $$ | |
| ① | $$ 7 \sqrt{84} =
7 \sqrt{ 2 ^2 \cdot 21 } =
7 \sqrt{ 2 ^2 } \, \sqrt{ 21 } =
7 \cdot 2 \sqrt{ 21 } =
14 \sqrt{ 21 } $$ |
| ② | Combine like terms |
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