Answer
$$\frac{11}{3\sqrt{5}+1}=\frac{3\sqrt{5}-1}{4}$$
Explanation
Tap the blue circles to see an explanation.
| $$ \begin{aligned}\frac{11}{3\sqrt{5}+1}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}\frac{11}{3\sqrt{5}+1}\frac{3\sqrt{5}-1}{3\sqrt{5}-1} \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}\frac{33\sqrt{5}-11}{45-3\sqrt{5}+3\sqrt{5}-1} \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle3}{\textcircled {3}} } }}}\frac{33\sqrt{5}-11}{44} \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle4}{\textcircled {4}} } }}}\frac{3\sqrt{5}-1}{4}\end{aligned} $$ | |
| ① | Multiply the numerator and denominator by the conjugate of the denominator . $$\color{blue}{ 3 \sqrt{5}-1} $$. |
| ② | Multiply in a numerator. $$ \color{blue}{ 11 } \cdot \left( 3 \sqrt{5}-1\right) = \color{blue}{11} \cdot 3 \sqrt{5}+\color{blue}{11} \cdot-1 = \\ = 33 \sqrt{5}-11 $$ Simplify denominator. $$ \color{blue}{ \left( 3 \sqrt{5} + 1\right) } \cdot \left( 3 \sqrt{5}-1\right) = \color{blue}{ 3 \sqrt{5}} \cdot 3 \sqrt{5}+\color{blue}{ 3 \sqrt{5}} \cdot-1+\color{blue}{1} \cdot 3 \sqrt{5}+\color{blue}{1} \cdot-1 = \\ = 45- 3 \sqrt{5} + 3 \sqrt{5}-1 $$ |
| ③ | Simplify numerator and denominator |
| ④ | Divide both numerator and denominator by 11. |
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