Question
Answer
$$\dfrac{9}{1+\sqrt{10}}=-1+\sqrt{10}$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}\frac{9}{1+\sqrt{10}}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}\frac{9}{1+\sqrt{10}}\frac{1-\sqrt{10}}{1-\sqrt{10}} \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}\frac{9-9\sqrt{10}}{1-\sqrt{10}+\sqrt{10}-10} \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle3}{\textcircled {3}} } }}}\frac{9-9\sqrt{10}}{-9} \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle4}{\textcircled {4}} } }}}\frac{1-\sqrt{10}}{-1} \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle5}{\textcircled {5}} } }}}\frac{-1+\sqrt{10}}{1} \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle6}{\textcircled {6}} } }}}-1+\sqrt{10}\end{aligned} $$ | |
| ① | Multiply the numerator and denominator by the conjugate of the denominator . $$\color{blue}{ 1- \sqrt{10}} $$. |
| ② | Multiply in a numerator. $$ \color{blue}{ 9 } \cdot \left( 1- \sqrt{10}\right) = \color{blue}{9} \cdot1+\color{blue}{9} \cdot- \sqrt{10} = \\ = 9- 9 \sqrt{10} $$ Simplify denominator. $$ \color{blue}{ \left( 1 + \sqrt{10}\right) } \cdot \left( 1- \sqrt{10}\right) = \color{blue}{1} \cdot1+\color{blue}{1} \cdot- \sqrt{10}+\color{blue}{ \sqrt{10}} \cdot1+\color{blue}{ \sqrt{10}} \cdot- \sqrt{10} = \\ = 1- \sqrt{10} + \sqrt{10}-10 $$ |
| ③ | Simplify numerator and denominator |
| ④ | Divide both numerator and denominator by 9. |
| ⑤ | Multiply both numerator and denominator by -1. |
| ⑥ | Remove 1 from denominator. |
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