Answer
$$\frac{7}{3+\sqrt{2}}=3-\sqrt{2}$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}\frac{7}{3+\sqrt{2}}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}\frac{7}{3+\sqrt{2}}\frac{3-\sqrt{2}}{3-\sqrt{2}} \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}\frac{21-7\sqrt{2}}{9-3\sqrt{2}+3\sqrt{2}-2} \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle3}{\textcircled {3}} } }}}\frac{21-7\sqrt{2}}{7} \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle4}{\textcircled {4}} } }}}\frac{3-\sqrt{2}}{1} \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle5}{\textcircled {5}} } }}}3-\sqrt{2}\end{aligned} $$ | |
| ① | Multiply the numerator and denominator by the conjugate of the denominator . $$\color{blue}{ 3- \sqrt{2}} $$. |
| ② | Multiply in a numerator. $$ \color{blue}{ 7 } \cdot \left( 3- \sqrt{2}\right) = \color{blue}{7} \cdot3+\color{blue}{7} \cdot- \sqrt{2} = \\ = 21- 7 \sqrt{2} $$ Simplify denominator. $$ \color{blue}{ \left( 3 + \sqrt{2}\right) } \cdot \left( 3- \sqrt{2}\right) = \color{blue}{3} \cdot3+\color{blue}{3} \cdot- \sqrt{2}+\color{blue}{ \sqrt{2}} \cdot3+\color{blue}{ \sqrt{2}} \cdot- \sqrt{2} = \\ = 9- 3 \sqrt{2} + 3 \sqrt{2}-2 $$ |
| ③ | Simplify numerator and denominator |
| ④ | Divide both numerator and denominator by 7. |
| ⑤ | Remove 1 from denominator. |
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