Ответ будет таким (x1, y1) =(1, 2) (x2, y2) =(23/8,-7/4)
1)Г
2)А
Надеюсь полное решение не нужно )
1. cos(4a-2a)=cos2a
2. cos(a-a-b)=cosb
2a^2+2ab-2ac-2ab+2b^2+2bc+2ac-2ab+2c^2
2Cos²x - 5Cosx + 3 = 0
Сделаем замену :
Cosx = m , - 1 ≤ m ≤ 1
2m² - 5m + 3 = 0
D = (- 5)² - 4 * 2 * 3 = 25 - 24 = 1
![m_{1}=\frac{5-1}{4}=1\\\\m_{2}=\frac{5+1}{4}=1,5>1](https://tex.z-dn.net/?f=m_%7B1%7D%3D%5Cfrac%7B5-1%7D%7B4%7D%3D1%5C%5C%5C%5Cm_%7B2%7D%3D%5Cfrac%7B5%2B1%7D%7B4%7D%3D1%2C5%3E1)
![Cosx=1\\\\x=2\pi n,n\in z](https://tex.z-dn.net/?f=Cosx%3D1%5C%5C%5C%5Cx%3D2%5Cpi+n%2Cn%5Cin+z)