Question

Сделать 1 вариант срочно​

Answer 1

$\displaystyle \tt 1). \ \ 2\frac{1}{3}-4:\bigg(3\frac{2}{5}+9,8\bigg)=2\frac{1}{3}-4:13,2=\frac{7}{3}-\frac{10}{33}=\frac{77-10}{33}=2\frac{1}{33};\\\\\\2). \ \ \bigg(1-\frac{a-3b}{2a}\bigg)\bigg(\frac{1}{a+3b}+\frac{1}{a-3b}\bigg)=\frac{a+3b}{2a}\cdot\frac{a-3b+a+3b}{(a+3b)(a-3b)}=\frac{1}{a-3b};$

$\displaystyle \tt 3).\ \ \sqrt{x^{2}-2x-63};\\\\x^{2}-2x-63\geq 0 \ \ \ \ \ \ \ D=b^{2}-4ac=4+252=256=16^{2}\\\\x_{1}=9\\x_{2}=-7\\\\\\(x-9)(x+7)\geq 0\\\\x\leq -7\\x\geq 9\\\\x\in(-\infty;-7]\cup[9;\infty)$