<span> (4х+5)(3-х)=х^2 - 2х</span>
<span>23x - 4x^2 +15 - 5x - x^2 +2x = 0</span>
<span>-5x^2 +20x+15 = 0</span>
<span>-x^2 + 4x +3=0</span>
<span>a = -1</span>
<span>b = 4</span>
c = 3
![\left \{ {{x-2y=0} \atop {5xy+y^2=44}} \right. \left \{ {{x=2y} \atop {5xy+y^2=44}} \right.](https://tex.z-dn.net/?f=%5Cleft+%5C%7B+%7B%7Bx-2y%3D0%7D+%5Catop+%7B5xy%2By%5E2%3D44%7D%7D+%5Cright.+%5Cleft+%5C%7B+%7B%7Bx%3D2y%7D+%5Catop+%7B5xy%2By%5E2%3D44%7D%7D+%5Cright.)
Подставим первое уравнение во второе и отдельно его решим
![5(2y)y+y^2=44 \\ 10y^2+y^2=44 \\ 11y^2=44|:11 \\ y^2=4 \\ y=\sqrt{4} \\ y=+-2](https://tex.z-dn.net/?f=5%282y%29y%2By%5E2%3D44+%5C%5C+10y%5E2%2By%5E2%3D44+%5C%5C+11y%5E2%3D44%7C%3A11+%5C%5C+y%5E2%3D4+%5C%5C+y%3D%5Csqrt%7B4%7D+%5C%5C+y%3D%2B-2+)
Вернемся в систему которых теперь будет две
![1. \left \{ {{x=2y} \atop {y=2}} \right. \left \{ {{x=2*2} \atop {y=2}} \right. \left \{ {{x=4} \atop {y=2}} \right. \\2. \left \{ {{x=2y} \atop {y=-2}} \right. \left \{ {{x=2*(-2)} \atop {y=-2}} \right. \left \{ {{x=-4} \atop {y=-2}} \right.](https://tex.z-dn.net/?f=1.+%5Cleft+%5C%7B+%7B%7Bx%3D2y%7D+%5Catop+%7By%3D2%7D%7D+%5Cright.++%5Cleft+%5C%7B+%7B%7Bx%3D2%2A2%7D+%5Catop+%7By%3D2%7D%7D+%5Cright.++%5Cleft+%5C%7B+%7B%7Bx%3D4%7D+%5Catop+%7By%3D2%7D%7D+%5Cright.+%5C%5C2.+%5Cleft+%5C%7B+%7B%7Bx%3D2y%7D+%5Catop+%7By%3D-2%7D%7D+%5Cright.++%5Cleft+%5C%7B+%7B%7Bx%3D2%2A%28-2%29%7D+%5Catop+%7By%3D-2%7D%7D+%5Cright.++%5Cleft+%5C%7B+%7B%7Bx%3D-4%7D+%5Catop+%7By%3D-2%7D%7D+%5Cright.+)
Ответ(4:2) и (-4:-2)
9 2/7 = (9*7 + 2)/7 = 65/7
1 7/9 = (1*9 + 7)/9 = 16/9
2 2/5 = (5*2 + 2)/5 = 12/5
1 1/3 = (1*3 + 1)/3 = 4/3
65/7 + 16/9 : (12/5 - 4/3) * 3/7 =
= 65/7 + 16/9 * 15/16 * 3/7 =
= 65/7 + 15/21 =
= 195/21 + 15/21 =
= 210/21 = 10
P = 12П (пи) или P~37,69911
1. из 1 уравнения выразим у:
у=1-3х, подставим во второе уравнение:
2х - 3(1 -3х) =8
2х -3 +9х=8
2х+9х =8+3
11х =11
х =1
у= 1 -3·1 = -2
Ответ: х=1; у = -2
2. из 1 уравнения выразим у
у = 2х - 5
подставим во второе уравнение:
3х-4(2х-5)=2
3х-8х+20=2
-5х=-18
х=3,6
найдем у
у = 2·3,6 - 5 =7,2 - 5 =2,2
Ответ: х=3,6; у =2,2