Question
Answer
$$(\sqrt{5}+2)(-2\sqrt{5}-5)=-20-9\sqrt{5}$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}(\sqrt{5}+2)(-2\sqrt{5}-5)& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}-10-5\sqrt{5}-4\sqrt{5}-10 \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}-20-9\sqrt{5}\end{aligned} $$ | |
| ① | $$ \color{blue}{ \left( \sqrt{5} + 2\right) } \cdot \left( - 2 \sqrt{5}-5\right) = \color{blue}{ \sqrt{5}} \cdot- 2 \sqrt{5}+\color{blue}{ \sqrt{5}} \cdot-5+\color{blue}{2} \cdot- 2 \sqrt{5}+\color{blue}{2} \cdot-5 = \\ = -10- 5 \sqrt{5}- 4 \sqrt{5}-10 $$ |
| ② | Combine like terms |
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