2) а^2=c^2-b^2
у(by+4b)+(cy-4c+4b)
yb(y+4)+c(y-4+4b)
2cos x + √2=0
2cos x = - √2
cos x = - √2/2
x = +- 3π/4 + 2πn, n∈Z
Г.-3π/4∈[π; 2π]
Б. 5π/4∈[π; 2π][