设等差数列{an}(n∈正整数)的前n项和为Sn,该数列是单调递增数列,若S4≥10,S5≤15,则a4的取值范围
设等差数列{an}(n∈正整数)的前n项和为Sn,该数列是单调递增数列,若S4≥10,S5≤15,则a4的取值范围
设等差数列{an}的前n项和为Sn,若S4≥10,S5≤15,则a4的最大值为______.
设等差数列an的前n项和为Sn,若S4>=10,S5
设数列(An)是等差数列,且a2=-6,a8=6,Sn是数列(An)的前n项和,求S4,S5,S6.
设数列{an}是公差不为0的等差数列,Sn是数列{an}的前n项和,若S1,S2,S4成等比数列,则a4/a1=?
设等差数列{an}的前n项和为Sn,若a5=5a3,则S4/S5
设等差数列{an}的前n项和为Sn,若S2=4,S4=20,则该数列的公差d等于多少?
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
已知等差数列{An}中,Sn是它前n项和,设A4=-2,S5=-20.求数列{an}的通项公式?
设Sn是等差数列{an}的前n项和,若a4=9,S3=15,则数列{an}的通项为______.
数列{an}是等差数列,Sn是前n项和,a4=3,S5=25
设数列{an}的前n项和为Sn,若对任意正整数,都有Sn=n(a1+an)/2,证明{an}是等差数列.