x^2(x-6)-4(x-6)=0
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