Question

Срочно! даю 22 балла!!!

Answer 1

Ответ:

8.

$\frac{f}{ \sqrt{21} } \times \frac{ \sqrt{21} }{ \sqrt{21} } = \frac{f \sqrt{21} }{21}$

9.

$\frac{4}{3 \sqrt{19} } \times \frac{ \sqrt{19} }{ \sqrt{19} } = \frac{4 \sqrt{19} }{3 \times 19} = \frac{4 \sqrt{19} }{57}$

10.

$\frac{20}{3 + 2 \sqrt{2} } \times \frac{3 - 2 \sqrt{2} }{3 - 2 \sqrt{2} } = \frac{20(3 - 2 \sqrt{2} )}{ {3}^{2} - {(2 \sqrt{2} )}^{2} } = \\ = \frac{60 - 40 \sqrt{2} }{9 - 8} = 60 - 40 \sqrt{2}$