7x-4-5(x-6)=0
7x-4-(5x-30)=0
7x-4-5x+30=0
2x-4+30=0
2x+26=0
x=-26/2
x=-13
![\left \{ {{2x - y = 13} \atop {2x + 3y=9}} \right.](https://tex.z-dn.net/?f=+%5Cleft+%5C%7B+%7B%7B2x+-+y+%3D+13%7D+%5Catop+%7B2x+%2B+3y%3D9%7D%7D+%5Cright.+)
Из первого уравнения вычесть второе
![\left \{ {{- 4y = 4} \atop {2x + 3y=9}} \right. \\ \\ \left \{ {{y = -1} \atop {2x + 3*(-1)=9}} \right. \\ \\ \left \{ {{y = -1} \atop {2x =12}} \right. \\ \\ \left \{ {{y = -1} \atop {x =6}} \right.](https://tex.z-dn.net/?f=+%5Cleft+%5C%7B+%7B%7B-+4y+%3D+4%7D+%5Catop+%7B2x+%2B+3y%3D9%7D%7D+%5Cright.++%5C%5C++%5C%5C++%5Cleft+%5C%7B+%7B%7By+%3D+-1%7D+%5Catop+%7B2x+%2B+3%2A%28-1%29%3D9%7D%7D+%5Cright.++%5C%5C++%5C%5C+%5Cleft+%5C%7B+%7B%7By+%3D+-1%7D+%5Catop+%7B2x+%3D12%7D%7D+%5Cright.+%5C%5C++%5C%5C+%5Cleft+%5C%7B+%7B%7By+%3D+-1%7D+%5Catop+%7Bx+%3D6%7D%7D+%5Cright.)
Ответ: (6; -1)
Значение функции будет равно -2 при значении х = -2
4 x² - 11x + 6 = 0
D = 121 - 96 = 25
X1,2 = 11+-5 / 8
X1 = 11-5 / 8 = 0,75
X2 = 11+5 / 8 = 2