х²+6х-1=0
Д=36+4*1=40>0- 2 корня
cos(2x+π/6)> √2/2
x1+x2=b/2
x1*x2=-c/2
3+c=b/2
3c=-c/2
c=0
b/2=3
b=6
b) -2+b=b/2 b/2=2 b=4
-2*b=-c/2 -8=-c/2 c=16