Question

Любой номер дайте пажалуйсто

Answer 1

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


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


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

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