Сначала умножим все уравнение на 2, получим: 3y+10=y
2y=-10
y=-5
4х2-(4х-1)(Х+5)
4х2-(4х2+20х-х-5)
4х2-4х2-20х+х+5
-19х+5
![\left \{ {{ \frac{1}{x+y-1} +\frac{1}{x-y+1}=1} \atop {\frac{5}{x+y-1}}-\frac{3}{x-y+1}=1} \right.](https://tex.z-dn.net/?f=+%5Cleft+%5C%7B+%7B%7B+%5Cfrac%7B1%7D%7Bx%2By-1%7D+%2B%5Cfrac%7B1%7D%7Bx-y%2B1%7D%3D1%7D+%5Catop+%7B%5Cfrac%7B5%7D%7Bx%2By-1%7D%7D-%5Cfrac%7B3%7D%7Bx-y%2B1%7D%3D1%7D+%5Cright.+)
пусть
![\frac{1}{x+y-1}=t \\ \frac{1}{x-y+-1}=u](https://tex.z-dn.net/?f=%5Cfrac%7B1%7D%7Bx%2By-1%7D%3Dt+%5C%5C+%5Cfrac%7B1%7D%7Bx-y%2B-1%7D%3Du)
тогда
![\left \{ {{t+u=1} \atop {5t-3u=1}} \right. \\ \\ (t;u)=( \frac{1}{2} ; \frac{1}{2} )](https://tex.z-dn.net/?f=+%5Cleft+%5C%7B+%7B%7Bt%2Bu%3D1%7D+%5Catop+%7B5t-3u%3D1%7D%7D+%5Cright.++%5C%5C++%5C%5C+%28t%3Bu%29%3D%28+%5Cfrac%7B1%7D%7B2%7D+%3B+%5Cfrac%7B1%7D%7B2%7D+%29)
подставим значения
![\left \{ {{\frac{1}{x+y-1}= \frac{1}{2} } \atop {\frac{1}{x-y+1}}= \frac{1}{2} } \right. \\ \\ (x;y)=(2;1)](https://tex.z-dn.net/?f=+%5Cleft+%5C%7B+%7B%7B%5Cfrac%7B1%7D%7Bx%2By-1%7D%3D+%5Cfrac%7B1%7D%7B2%7D+%7D+%5Catop+%7B%5Cfrac%7B1%7D%7Bx-y%2B1%7D%7D%3D+%5Cfrac%7B1%7D%7B2%7D+%7D+%5Cright.++%5C%5C++%5C%5C+%28x%3By%29%3D%282%3B1%29)
произведение корней равно 2
Сначала сократим дроби
21/14=3/2=1 1/2
4/18=2/9
7/2=3 1/2
5/10=1/2
8/36=2/9
18/24=3/4
4/8=1/2
Теперь видно,что 5/10=4/8, а 4/18=8/36