30 баллов 1 вариант Пожалуйста

1)
$3\sqrt{7}=\sqrt{3^2*7}=\sqrt{63}\\4\sqrt{5}=\sqrt{4^2*5}=\sqrt{80}\\3\sqrt{7}<4\sqrt{5}$

2)
$=\frac{(\sqrt{3})^2-\sqrt{3}}{2\sqrt{3}}=\frac{\sqrt{3}(\sqrt{3}-1)}{2\sqrt{3}}=\frac{\sqrt{3}-1}{2}$

$\frac{4b-2}{2\sqrt{b}-\sqrt{2}}=\frac{(2\sqrt{b})^2-(\sqrt{2})^2}{2\sqrt{b}-\sqrt{2}}=\frac{(2\sqrt{b}-\sqrt{2})*(2\sqrt{b}+\sqrt{2})}{2\sqrt{b}-\sqrt{2}}=2\sqrt{b}+\sqrt{2}$

3)
a)
$\frac{2}{\sqrt{7}}=\frac{2*\sqrt{7}}{\sqrt{7}*\sqrt{7}}=\frac{2\sqrt{7}}{7}$

б)
$\frac{\sqrt{2}}{\sqrt{2}+1}=\frac{\sqrt{2}*(\sqrt{2}-1)}{(\sqrt{2}+1)*(\sqrt{2}-1)}=\frac{\sqrt{4}-\sqrt{2}}{(\sqrt{2})^2-1^2}=2-\sqrt{2}$