设等比数列{an}前n项的和为Sn,已知an=5Sn-3,则公比q=
1个回答
an=5Sn-3
a(n-1)=5S(n-1)-3
相减,Sn-S(n-1)=an
an-a(n-1)=5an
an/a(n-1)=-1/4
所以q=-1/4
相关问题
等比数列{an}前n项和为Sn,诺an+1=5Sn+1,则公比q=?
设等比数列{an}的公比为q,前n项和为Sn,若Sn+1,Sn,Sn+2成等差数列,则公比q为( )
设等比数列{ an}的公比为q,q>0且q≠1,Sn为{an}的前n项和,记Tn=an/Sn,则
设等比数列{an}的公比为q,前n项和为Sn,求数列{Sn}的前n项和Un
已知公比为q(q≠1)的等比数列{an}的前n项和为Sn,则数列{1/an}的前n项和为_____?
等比数列{an}的公比为q,前n项和为Sn
设等比数列{an}的公比为q,前n项和为Sn,若Sn+1,Sn,Sn+2成等差数列,则q的值为
设{an}是公比为q的等比数列,Sn是它的前n项和.若{Sn}是等差数列,则q=______.
设{an}是公比为q的等比数列,Sn是它的前n项和.若{Sn}是等差数列,则q=______.
设{an}是公比为q的等比数列,Sn是它的前n项和.若{Sn}是等差数列,则q=______.