Question
Answer
$$\dfrac{7}{10\sqrt{2}+\sqrt{10}}=\dfrac{70\sqrt{2}-7\sqrt{10}}{190}$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}\frac{7}{10\sqrt{2}+\sqrt{10}}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}\frac{7}{10\sqrt{2}+\sqrt{10}}\frac{10\sqrt{2}-\sqrt{10}}{10\sqrt{2}-\sqrt{10}} \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}\frac{70\sqrt{2}-7\sqrt{10}}{200-20\sqrt{5}+20\sqrt{5}-10} \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle3}{\textcircled {3}} } }}}\frac{70\sqrt{2}-7\sqrt{10}}{190}\end{aligned} $$ | |
| ① | Multiply the numerator and denominator by the conjugate of the denominator . $$\color{blue}{ 10 \sqrt{2}- \sqrt{10}} $$. |
| ② | Multiply in a numerator. $$ \color{blue}{ 7 } \cdot \left( 10 \sqrt{2}- \sqrt{10}\right) = \color{blue}{7} \cdot 10 \sqrt{2}+\color{blue}{7} \cdot- \sqrt{10} = \\ = 70 \sqrt{2}- 7 \sqrt{10} $$ Simplify denominator. $$ \color{blue}{ \left( 10 \sqrt{2} + \sqrt{10}\right) } \cdot \left( 10 \sqrt{2}- \sqrt{10}\right) = \color{blue}{ 10 \sqrt{2}} \cdot 10 \sqrt{2}+\color{blue}{ 10 \sqrt{2}} \cdot- \sqrt{10}+\color{blue}{ \sqrt{10}} \cdot 10 \sqrt{2}+\color{blue}{ \sqrt{10}} \cdot- \sqrt{10} = \\ = 200- 20 \sqrt{5} + 20 \sqrt{5}-10 $$ |
| ③ | Simplify numerator and denominator |
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