Игрек равняется 0,8 плюс 5 игрек равно 5,8 игрек равно 2,7 минус 14 игрек равно минус 16,7
По ВИЕТУ x1+x2=-b=6 x1*x2=c=2 x1/x2+x2/x1+2=(x1²+x2²)/x1x2+2
x1²+x2²=(x1+x2)²-2x1x2=36-4=32
... =32/2+2=18
(x1+x2)²-2x1*x2)/x1*x2+2
15x²+19x+4=0
D=19²-4*4*15=361-240=121=11²
![x_{1}= \frac{-19- \sqrt{121} }{2*15} = \frac{-19- 11 }{30} = \frac{-30}{30} =-1 \\ x_{2}= \frac{-19+ \sqrt{121} }{2*15}= \frac{-19+ 11 }{30} = \frac{-8}{30} =- \frac{4}{15}](https://tex.z-dn.net/?f=x_%7B1%7D%3D+%5Cfrac%7B-19-+%5Csqrt%7B121%7D+%7D%7B2%2A15%7D+%3D+%5Cfrac%7B-19-+11+%7D%7B30%7D+%3D+%5Cfrac%7B-30%7D%7B30%7D+%3D-1+%5C%5C+x_%7B2%7D%3D+%5Cfrac%7B-19%2B+%5Csqrt%7B121%7D+%7D%7B2%2A15%7D%3D++%5Cfrac%7B-19%2B+11+%7D%7B30%7D+%3D+%5Cfrac%7B-8%7D%7B30%7D+%3D-+%5Cfrac%7B4%7D%7B15%7D+)
x²-6x+8=0
x₁+x₂=-b
x₁x₂=c
x₁+x₂=6
x₁x₂=8
x₁=4
x₂=2
3x²=x+4
3x₂-x-4=0
D=(-1)²-4*(-4)*3=1+48=49=7²
![x_{1}= \frac{1- \sqrt{49} }{2*3} = \frac{1-7}{6} = \frac{-6}{6} =-1 \\ x_{2}= \frac{1+ \sqrt{49} }{2*3} = \frac{1+7}{6} = \frac{8}{6} = \frac{4}{3} ](https://tex.z-dn.net/?f=x_%7B1%7D%3D+%5Cfrac%7B1-+%5Csqrt%7B49%7D+%7D%7B2%2A3%7D+%3D+%5Cfrac%7B1-7%7D%7B6%7D+%3D+%5Cfrac%7B-6%7D%7B6%7D+%3D-1+%5C%5C+x_%7B2%7D%3D+%5Cfrac%7B1%2B+%5Csqrt%7B49%7D+%7D%7B2%2A3%7D+%3D+%5Cfrac%7B1%2B7%7D%7B6%7D+%3D+%5Cfrac%7B8%7D%7B6%7D+%3D+%5Cfrac%7B4%7D%7B3%7D+%0A)
4x²+x-5=0
D=1-4*(-5)*4=1+80=81=9²
![x_{1}= \frac{-1- \sqrt{81} }{2*4} = \frac{-1-9}{8} = \frac{-10}{8} =-1,25 \\ x_{2}= \frac{-1+ \sqrt{81} }{2*4} = \frac{-1+9}{8} = \frac{8}{8} =1](https://tex.z-dn.net/?f=x_%7B1%7D%3D+%5Cfrac%7B-1-+%5Csqrt%7B81%7D+%7D%7B2%2A4%7D+%3D+%5Cfrac%7B-1-9%7D%7B8%7D+%3D+%5Cfrac%7B-10%7D%7B8%7D+%3D-1%2C25+%5C%5C+x_%7B2%7D%3D+%5Cfrac%7B-1%2B+%5Csqrt%7B81%7D+%7D%7B2%2A4%7D+%3D+%5Cfrac%7B-1%2B9%7D%7B8%7D+%3D+%5Cfrac%7B8%7D%7B8%7D+%3D1)
2x²-6x+5=0
D=(-6)²-4*5*2=36-40= - 4<0
D<0 - корней нет.
Г) 7 и 42,число 126 делится на них без остатка