Tap the blue circles to see an explanation.
$$ \begin{aligned}\sqrt{-216}& \xlongequal{ }\sqrt{216}\cdot i \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}} \sqrt{ 36 \cdot 6 } i \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}} \sqrt{ 36 } \cdot \sqrt{ 6 } i \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle3}{\textcircled {3}} } }}}6\sqrt{6}i\end{aligned} $$ | |
① | Factor out the largest perfect square of 216. ( in this example we factored out $ 36 $ ) |
② | Rewrite $ \sqrt{ 36 \cdot 6 } $ as the product of two radicals. |
③ | The square root of $ 36 $ is $ 6 $. |