数列an的前n项的和sn,当n≥1时,s(n+1)是a(n+1)与s(n+1)+2的等比中项求证：数列｛1/sn｝为等差数列当a1=-1时,求an

数列an的前n项的和sn,当n≥1时,s(n+1)是a(n+1)与s(n+1)+2的等比中项求证：数列｛1/sn｝为等差数列当a1=-1时,求an
数列an的前n项的和sn,当n≥1时,s(n+1)是a(n+1)与s(n+1)+2的等比中项
求证：数列｛1/sn｝为等差数列
当a1=-1时,求an

数列an的前n项的和sn,当n≥1时,s(n+1)是a(n+1)与s(n+1)+2的等比中项求证：数列｛1/sn｝为等差数列当a1=-1时,求an
,s(n+1)是a(n+1)与s(n+1)+2的等比中项 ==》》a(n+1)*（s(n+1)+2）=s(n+1)^2
a(n+1)=s(n+1)-sn
(s(n+1)-sn)*（s(n+1)+2）=s(n+1)^2
2s(n+1)-sn*s(n+1)-2sn=0
1/s(n+1)-1/sn=-1/2
数列｛1/sn｝为等差数列
1/sn=1/s1-1/2(n-1)=-1--1/2(n-1)=-(n+3)/2