a2*a44=a9^2
a2+a9+a44=217
(a1+d)(a1+43d)=(a1+8d)^2 --->28a1d=21d^2--->a1=3d/4 or d=0
a1+d+a1+8d+a1+43d=217----3a1+52d=217
a1=3,d=2 三个数分别为 7 35 175---->q=5
{An}的公比q=5,设其首项A1=a,则A2=aq=5a,Sn=a[(5^n)-1]/4,∴ Sn/A2=[(5^n)-1]/20,由6/5
a2*a44=a9^2
a2+a9+a44=217
(a1+d)(a1+43d)=(a1+8d)^2 --->28a1d=21d^2--->a1=3d/4 or d=0
a1+d+a1+8d+a1+43d=217----3a1+52d=217
a1=3,d=2 三个数分别为 7 35 175---->q=5
{An}的公比q=5,设其首项A1=a,则A2=aq=5a,Sn=a[(5^n)-1]/4,∴ Sn/A2=[(5^n)-1]/20,由6/5