A1+a2+a3=18
a1+a1+d+a1+2d=18
3a1+3d=18
a1+d=6
a2=6
a1=6-d
a3=6+d
b1=6-d+1=7-d
b2=6+4=10
b3=6+d+12=18+d
q=b2/b1=b3/b2
10/(7-d)=(18+d)/10
100=(7-d)*(18+d)
100-126-7d+18d+d²=0
d²+11d-26=0
D=121+104=225
d1=(-11-15)/2=-13 не удов усл
d2=(-11+15)/2=2
a1=6-2=4
a3=6+2=8
a1*a2*a3=4*6*8=192