Помогите пожалуйста 3 и 5 задание с подробным решением.

Question 1

Question 2

Это 9-тый класс?

Question 3

Решите задачу:

$(7^{\frac{1}2}-3^{\frac{1}2})^2+(7^{\frac{1}2}+3^{\frac{1}2})^2=(7^{\frac{1}2})^2-2*7^{\frac{1}2}*3^{\frac{1}2}+(3^{\frac{1}2})^2+(7^{\frac{1}2})^2+\\ +2*(7^{\frac{1}2})^2*3^{\frac{1}2}+(3^{\frac{1}2})^2=7^1+3^1+7^1+3^1=7+3+7+3=20$

$\big((\sqrt[4]{a}-\sqrt[4]{b})^{-2}+(\sqrt[4]{a}+\sqrt[4]{b})^{-2}\big):\frac{a^{\frac{1}2}+b^{\frac{1}2}}{a-b}=\\ \big(\frac{1}{(a^{\frac{1}4}-b^{\frac{1}4})^2}+\frac{1}{(a^{\frac{1}4}+b^{\frac{1}4})^{2}}\big):\frac{\sqrt a+\sqrt b}{(\sqrt a-\sqrt b)(\sqrt a+\sqrt b)}=\\ \big(\frac{1}{(a^{\frac{1}4}-b^{\frac{1}4})^2}+\frac{1}{(a^{\frac{1}4}+b^{\frac{1}4})^{2}}\big):\frac{1}{\sqrt a-\sqrt b}=$
$\big(\frac{\sqrt a-\sqrt b}{(a^{\frac{1}4}-b^{\frac{1}4})^2}+\frac{\sqrt a-\sqrt b}{(a^{\frac{1}4}+b^{\frac{1}4})^{2}}\big)=\\ \big(\frac{a^{\frac{1}2}-b^{\frac{1}2}}{(a^{\frac{1}4}-b^{\frac{1}4})^2}+\frac{a^{\frac{1}2}-b^{\frac{1}2}}{(a^{\frac{1}4}+b^{\frac{1}4})^{2}}\big)=\\ \big(\frac{(a^{\frac{1}4}-b^{\frac{1}4})(a^{\frac{1}4}+b^{\frac{1}4})}{(a^{\frac{1}4}-b^{\frac{1}4})^2}+\frac{(a^{\frac{1}4}-b^{\frac{1}4})(a^{\frac{1}4}+b^{\frac{1}4})}{(a^{\frac{1}4}+b^{\frac{1}4})^{2}}\big)=$
$\frac{a^{\frac{1}4}+b^{\frac{1}4}}{a^{\frac{1}4}-b^{\frac{1}4}}+\frac{a^{\frac{1}4}-b^{\frac{1}4}}{a^{\frac{1}4}+b^{\frac{1}4}}=$
$\frac{(a^{\frac{1}4}+b^{\frac{1}4})(a^{\frac{1}4}+b^{\frac{1}4})}{(a^{\frac{1}4}-b^{\frac{1}4})(a^{\frac{1}4}+b^{\frac{1}4})}+\frac{(a^{\frac{1}4}-b^{\frac{1}4})(a^{\frac{1}4}-b^{\frac{1}4})}{(a^{\frac{1}4}+b^{\frac{1}4})(a^{\frac{1}4}-b^{\frac{1}4})}=\\ \frac{(a^{\frac{1}4}+b^{\frac{1}4})^2+(a^{\frac{1}4}-b^{\frac{1}4})^2}{a^{\frac{1}2}-b^{\frac{1}2}}=\frac{a^{\frac{1}2}+2a^{\frac{1}4}b^{\frac{1}4}+b^{\frac{1}2}+a^{\frac{1}2}-2a^{\frac{1}4}b^{\frac{1}4}+b^{\frac{1}2}}{a^{\frac{1}2}-b^{\frac{1}2}}=$
$=\frac{a^{\frac{1}2}+2a^{\frac{1}4}b^{\frac{1}4}+b^{\frac{1}2}+a^{\frac{1}2}-2a^{\frac{1}4}b^{\frac{1}4}+b^{\frac{1}2}}{a^{\frac{1}2}-b^{\frac{1}2}}=\\ =\frac{2a^{\frac{1}2}+2b^{\frac{1}2}}{a^{\frac{1}2}-b^{\frac{1}2}}=\frac{2(a^{\frac{1}2}+b^{\frac{1}2})(a^{\frac{1}2}-b^{\frac{1}2})}{(a^{\frac{1}2}-b^{\frac{1}2})^2}=\frac{2(a-b)}{(a^{\frac{1}2}-b^{\frac{1}2})^2}\\$