Tap the blue circles to see an explanation.
| $$ \begin{aligned}-\sqrt{10}-2\sqrt{90}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-\sqrt{10}-6\sqrt{10} \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-7\sqrt{10}\end{aligned} $$ | |
| ① | $$ - 2 \sqrt{90} =
-2 \sqrt{ 3 ^2 \cdot 10 } =
-2 \sqrt{ 3 ^2 } \, \sqrt{ 10 } =
-2 \cdot 3 \sqrt{ 10 } =
-6 \sqrt{ 10 } $$ |
| ② | Combine like terms |