3x-7y=16
6x+7y=11
9x=27
x=3
18+7y=11
7y=-7
y=-1
В: x=3 y=-1
(6y-1)²=36y²-12y+1
Формула: (a-b)²=a²-2ab+b²
1+2sinx=2cos2x
1+2sinx=2(1-2sin^2x)
1+2sinx=2-4sin^2x
4sin^2x+2sinx-1=0
sinx=(-1+-sqrt(5))/4 sinx>=0
sinx=(sqrt(5)-1)/4
x=(-1)^k*arcsin(sqrt(5)-1)/4)+Пk
sinx<0
1-2sinx=2-4sin^2x
4sin^2x-2sinx-1=0
x=(1+-sqrt(5))/4
x=1-sqrt(5))/4
x=(-1)^larcsin((1-sqrt(5)/4)+Пk