Question
Answer
$$\dfrac{1}{2\sqrt{2}+\sqrt{7}}=2\sqrt{2}-\sqrt{7}$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}\frac{1}{2\sqrt{2}+\sqrt{7}}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}\frac{1}{2\sqrt{2}+\sqrt{7}}\frac{2\sqrt{2}-\sqrt{7}}{2\sqrt{2}-\sqrt{7}} \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}\frac{2\sqrt{2}-\sqrt{7}}{8-2\sqrt{14}+2\sqrt{14}-7} \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle3}{\textcircled {3}} } }}}\frac{2\sqrt{2}-\sqrt{7}}{1} \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle4}{\textcircled {4}} } }}}2\sqrt{2}-\sqrt{7}\end{aligned} $$ | |
| ① | Multiply the numerator and denominator by the conjugate of the denominator . $$\color{blue}{ 2 \sqrt{2}- \sqrt{7}} $$. |
| ② | Multiply in a numerator. $$ \color{blue}{ 1 } \cdot \left( 2 \sqrt{2}- \sqrt{7}\right) = \color{blue}{1} \cdot 2 \sqrt{2}+\color{blue}{1} \cdot- \sqrt{7} = \\ = 2 \sqrt{2}- \sqrt{7} $$ Simplify denominator. $$ \color{blue}{ \left( 2 \sqrt{2} + \sqrt{7}\right) } \cdot \left( 2 \sqrt{2}- \sqrt{7}\right) = \color{blue}{ 2 \sqrt{2}} \cdot 2 \sqrt{2}+\color{blue}{ 2 \sqrt{2}} \cdot- \sqrt{7}+\color{blue}{ \sqrt{7}} \cdot 2 \sqrt{2}+\color{blue}{ \sqrt{7}} \cdot- \sqrt{7} = \\ = 8- 2 \sqrt{14} + 2 \sqrt{14}-7 $$ |
| ③ | Simplify numerator and denominator |
| ④ | Remove 1 from denominator. |
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