Х^2-5x-84=0
D=25+336=19^2
x1=(5+19)/2=12
x2=(5-19)/2=-7
8. x²-7x-18=0
D=121
![x_{1}= \frac{7-11}{2}=-2](https://tex.z-dn.net/?f=+x_%7B1%7D%3D+%5Cfrac%7B7-11%7D%7B2%7D%3D-2)
![x_{2}= \frac{7+11}{2}=9](https://tex.z-dn.net/?f=+x_%7B2%7D%3D+%5Cfrac%7B7%2B11%7D%7B2%7D%3D9)
Ответ: -2; 9
9.y=2x+8 и
![y= \frac{6-x}{2}](https://tex.z-dn.net/?f=y%3D+%5Cfrac%7B6-x%7D%7B2%7D+)
![2x+8=\frac{6-x}{2}](https://tex.z-dn.net/?f=2x%2B8%3D%5Cfrac%7B6-x%7D%7B2%7D)
⇒ 4x+16=6-x ⇒ 5x=-10 ⇒ x=-2 (абсцисса точки С)
7х-х^2=10
x^2-7x+10=0
D=9
x1=(7+3)/2=5
x2=(7-3)/2=2
1) (- беск;+беск) 2) (-беск;3/8] 3) (-беск;1/3) (1/3;1/2)(1/2;+беск)