q=b4/b3=-3/6=-1/2
b3=b1*q^2=6
b1*(-1/2)^2=6
b1=24
S=b1/(1-q)=24/(1+1/2)=24/1,5=16
....................................................................................................
1)x2+12x+32=0
2)x2+30x+200=0