I- x
II-y
x+y=26
5x+3y=108
x=26-y
5* (26-y)+3y=108
x=26-y
130-5y+3y=108
x=26-y
-2y=-22
x=26-y
y=11
x=26-11
y=11
x=15
![5-2x=11-7(x+2)](https://tex.z-dn.net/?f=5-2x%3D11-7%28x%2B2%29)
![5-2x=11-7x-14](https://tex.z-dn.net/?f=5-2x%3D11-7x-14)
![5-2x=-3-7x](https://tex.z-dn.net/?f=5-2x%3D-3-7x)
![7x-2x=-3-5](https://tex.z-dn.net/?f=7x-2x%3D-3-5)
![5x=-8](https://tex.z-dn.net/?f=5x%3D-8)
![x=-8:5](https://tex.z-dn.net/?f=x%3D-8%3A5)
![x=-\frac{8}{5}=-1,6](https://tex.z-dn.net/?f=x%3D-%5Cfrac%7B8%7D%7B5%7D%3D-1%2C6)
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(это проверка)
![5+3,2=11-7\cdot0,4](https://tex.z-dn.net/?f=5%2B3%2C2%3D11-7%5Ccdot0%2C4)
![8,2=11-2,8](https://tex.z-dn.net/?f=8%2C2%3D11-2%2C8)
![8,2=8,2](https://tex.z-dn.net/?f=8%2C2%3D8%2C2)
S=длина*ширина
S комнаты=5.85*3.5=20.475м² ~ 20.5м²
Ответ: 20.5м²
По формуле (a-b)^2=a^2+2ab+b^2
значит х^2-10х+25=(х-5)^2