Answer
$$7\sqrt{90}=21\sqrt{10}$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}7\sqrt{90}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}7\cdot \sqrt{ 9 \cdot 10 } \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}7\cdot \sqrt{ 9 } \cdot \sqrt{ 10 } \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle3}{\textcircled {3}} } }}}7\cdot3 \sqrt{ 10 } \xlongequal{ } \\[1 em] & \xlongequal{ }21\sqrt{10}\end{aligned} $$ | |
| ① | Factor out the largest perfect square of 90. ( in this example we factored out $ 9 $ ) |
| ② | Rewrite $ \sqrt{ 9 \cdot 10 } $ as the product of two radicals. |
| ③ | The square root of $ 9 $ is $ 3 $. |
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Simplify Radical Expression