Answer
$$2\sqrt{45}-\sqrt{20}+2\sqrt{5}=6\sqrt{5}$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}2\sqrt{45}-\sqrt{20}+2\sqrt{5}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}6\sqrt{5}-2\sqrt{5}+2\sqrt{5} \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle3}{\textcircled {3}} } }}}6\sqrt{5}\end{aligned} $$ | |
| ① | $$ 2 \sqrt{45} =
2 \sqrt{ 3 ^2 \cdot 5 } =
2 \sqrt{ 3 ^2 } \, \sqrt{ 5 } =
2 \cdot 3 \sqrt{ 5 } =
6 \sqrt{ 5 } $$ |
| ② | $$ - \sqrt{20} =
- \sqrt{ 2 ^2 \cdot 5 } =
- \sqrt{ 2 ^2 } \, \sqrt{ 5 } =
- 2 \sqrt{ 5 }$$ |
| ③ | Combine like terms |
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