Tap the blue circles to see an explanation.
$$ \begin{aligned}\frac{57}{5+\sqrt{6}}& \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle1}{\textcircled {1}} } }}}\frac{57}{5+\sqrt{6}}\frac{5-\sqrt{6}}{5-\sqrt{6}} \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle2}{\textcircled {2}} } }}}\frac{285-57\sqrt{6}}{25-5\sqrt{6}+5\sqrt{6}-6} \xlongequal{ } \\[1 em] & \xlongequal{ \color{blue}{ \text{\normalsize{ \htmlClass{explanationCircle explanationCircle3}{\textcircled {3}} } }}}\frac{285-57\sqrt{6}}{19}\end{aligned} $$ | |
① | Multiply the numerator and denominator by the conjugate of the denominator . $$\color{blue}{ 5- \sqrt{6}} $$. |
② | Multiply in a numerator. $$ \color{blue}{ 57 } \cdot \left( 5- \sqrt{6}\right) = \color{blue}{57} \cdot5+\color{blue}{57} \cdot- \sqrt{6} = \\ = 285- 57 \sqrt{6} $$ Simplify denominator. $$ \color{blue}{ \left( 5 + \sqrt{6}\right) } \cdot \left( 5- \sqrt{6}\right) = \color{blue}{5} \cdot5+\color{blue}{5} \cdot- \sqrt{6}+\color{blue}{ \sqrt{6}} \cdot5+\color{blue}{ \sqrt{6}} \cdot- \sqrt{6} = \\ = 25- 5 \sqrt{6} + 5 \sqrt{6}-6 $$ |
③ | Simplify numerator and denominator |