Question

Любой номер дайте пажалуйсто

Answer 1

4)
$sqrt{18x^3}=3|x|sqrt{2x}=3xsqrt{2x}$


5)
$frac{a^2-5b^2}{a+bsqrt{5}}=frac{(a-bsqrt{5})(a+bsqrt{5})}{a+bsqrt{5}}=a-bsqrt{5}$


6)
a)
$frac{3}{sqrt{21}}=frac{3*sqrt{21}}{sqrt{21}*sqrt{21}}=frac{3sqrt{21}}{21}=frac{sqrt{21}}{7}$

б)
$frac{1}{5-sqrt{7}}=frac{5+sqrt{7}}{(5-sqrt{7})(5+sqrt{7})}=frac{5+sqrt{7}}{5^2-(sqrt{7})^2}=frac{5+sqrt{7}}{18}$




7)
$frac{sqrt{x^2-2x+1}}{x-1}=frac{sqrt{(x-1)^2}}{x-1}=frac{|x-1|}{x-1}=frac{-(x-1)}{x-1}=-1$

Answer 2

спасибо большое