Question

$\frac{1}{5 - \sqrt{21} } \2$
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Answer 1

Answer:

$\frac{5+\sqrt{21} } {4}$

Step-by-step explanation:

$\frac{1}{5-\sqrt{21} }$

= $\frac{1}{5-\sqrt{21} } * \frac{5+\sqrt{21} } {5+\sqrt{21} }$

= $\frac{5+\sqrt{21} } {5^2-\sqrt{21}^2 }$

= $\frac{5+\sqrt{21} } {25-21 }$

= $\frac{5+\sqrt{21} } {4}$