已知{an}是等差数列,且{sn}是{an}的前n项和,a1,a3,a4成等比数列,求(s3-s2)/(s5-s3)的值快

已知{an}是等差数列,且{sn}是{an}的前n项和,a1,a3,a4成等比数列,求(s3-s2)/(s5-s3)的值快
已知{an}是等差数列,且{sn}是{an}的前n项和,a1,a3,a4成等比数列,求(s3-s2)/(s5-s3)的值
快

已知{an}是等差数列,且{sn}是{an}的前n项和,a1,a3,a4成等比数列,求(s3-s2)/(s5-s3)的值快
a1,a3,a4成等比数列
a3^2=a1*a4
a3^2=(a3-2d)*(a3+d)
a3^2=a3^2-2d^2-d*a3
d*(2d+a3)=0
d1=0
d2=-a3/2
d=0时
(s3-s2)/(s5-s3)
=a3/(a4+a5)
=1/2
d=-a3/2时
(s3-s2)/(s5-s3)
=a3/(a4+a5)
=a3/(2a3-3a3/2)
=1/(1/2)=2

1/2,设一下就搞定了，小题就直接都设为1