(3x²-7x+8)/(x²+1)<2
(3x²-7x+8)/(x²+1)-2<0
(3x²-7x+8-2x²-2)/(x²+1)<0
(x²-7x+6)/(x²+1)<0
x²+1>0 при любом х⇒x²-7x+6<0
x1+x2=7 U x1*x2=6⇒x1=1 U x2=6
x∈(1;6)
![\sqrt{-8+9x} =8](https://tex.z-dn.net/?f=+%5Csqrt%7B-8%2B9x%7D+%3D8)
ОДЗ: - 8 + 9х ≥ 0
9х ≥ 8
х ≥ 8/9
![( \sqrt{-8+9x} )^{2} = 8^{2}](https://tex.z-dn.net/?f=%28+%5Csqrt%7B-8%2B9x%7D+%29%5E%7B2%7D++%3D++8%5E%7B2%7D+)
- 8 + 9х = 64
9х = 72
х = 8
8 > 8/9 - корень отвечает ОДЗ
![\sqrt{9x-9} = 3](https://tex.z-dn.net/?f=+%5Csqrt%7B9x-9%7D+%3D+3)
ОДЗ: 9х - 9 ≥ 0
9х ≥ 9
х ≥ 1
![( \sqrt{9x-9} )^{2} = 3^{2}](https://tex.z-dn.net/?f=%28+%5Csqrt%7B9x-9%7D+%29%5E%7B2%7D+%3D++3%5E%7B2%7D+)
9х - 9 = 9
9х = 18
х = 2
2 > 1 - корень отвечает ОДЗ
![\sqrt{19+5x} =2](https://tex.z-dn.net/?f=+%5Csqrt%7B19%2B5x%7D+%3D2)
ОДЗ: 19 + 5х ≥ 0
5х ≥ - 19
х ≥ - 3 4/5
![(\sqrt{19+5x} )^{2} = 2^{2}](https://tex.z-dn.net/?f=+%28%5Csqrt%7B19%2B5x%7D+%29%5E%7B2%7D+%3D++2%5E%7B2%7D+)
19 + 5х = 4
5х = - 15
х = - 3
- 3 > - 3 4/5 - корень отвечает ОДЗ
-0,8.(c+5)-0,7(10c+5)+0,8c²+10c-4=
=-0,8c-4-7c-3,5+0,8c²+10c-4=0,8c²+(10c-7c-0,8c)+(-4-3,5-4)=
=0,8c²+2,2c-11,5