设等差数列{an}的前n项和为Sn,且S5=-5,S10=15,求数列{Sn/n}的前n项和Tn
设等差数列{an}的前n项和为Sn,且S5=-5,S10=15,求数列{Sn/n}的前n项和Tn
等差数列{an}的前n项和为Sn,且S5=-5,S10=15,求数列{Sn/n}的前n项和T
设Sn为等差数列{an}的前n项和,若S5=10,S10=—5,
设等比数列{an}的前n项和为Sn,若S10:S5=1:2,求S15:S5
设数列{an}前n项和为Sn,数列{Sn}的前n项和为Tn,满足Tn=2Sn-n2,n∈N*.
已知等差数列{an}的前n项和为sn,且满足s10=30,a5=10,(1)求数列{1/sn}的前n项和Tn
设等差数列an的前n项和为Sn,已知bn=1/Sn,且a3*b3=1/2,S3+S5=21,求bn,bn前n项和Tn.
设{an}是等差数列,{bn}是等比数列,记{an}{bn}的前n项和分别为Sn,Tn若a3=b3,a4=b4,且(S5
等差数列an的前n项和Sn,S5=5,S10=15,则S15=
已知数列{an}的前n项和为Sn,且对任意n属于N+有an+Sn=n,设Cn=n(1-bn)求数列{Cn}的前n项和Tn
设数列{an},{bn}都是等差数列,它们的前n项和分别为sn,Tn
设等差数列an的前n项和为Sn,若S4>=10,S5