已知等差数列an的前n项之和是Sn,则-am

已知等差数列an的前n项之和是Sn,则-am 已知等差数列﹛an﹜的前n项之和Sn=n^2,则an=_______. 1.已知等差数列{an}的前n项和为sn,若a5=18-a4,则s8等于?2.已知等差数列共有10项,其中奇数项之和为15,藕偶数项之和为30,则公差是?3.在等差数列{an}中,a1=-25,s3=s8,则前n项和sn的最小值为?4.等差数列{an} 已知公差为d的等差数列的前n项之和为Sn,则Sn+1/n+1-Sn/n 设sn 是等差数列{an} 的前n项之和,且s6s9 ,则下列结论中错误的①s9 (1)已知数列an的前n项和为sn满足sn=an²+bn,求证an是等差数列(2)已知等差数列an的前n项和为sn,求证数列sn/n也成等差数列 设{an}是等差数列,Sn是数列{an}的前n项之和,已知S7=7,S15=75,Tn是数列{Sn/n}的前n项和,求Tn 已知数列{an}的前n项和sn满足sn=an^2+bn,求证{an}是等差数列 设Sn是等差数列{an}的前n项和,已知S6=36,Sn=324,Sn-6=144（n>6),则n等于? 已知Sn为等差数列{an}的前n项之和,S9=18,Sn=256,a(n-4)=30（n〉9）,求n 设Sn为等差数列{An}的前n项和,求证：{Sn/n}是等差数列 已知sn=32n-n^2求等差数列|an|的前n项和sn 已知等差数列{an}的前n项和是sn=32n一n*n,求{|an|}的前n项和sn a1=1 an=2an-1+2n 求a2.a3 求证an/2n是等差数列 求数列an的前n项之和Sn ．已知数列的前n项之和为Sn=n2+3n,求证{an}为等差数列,若Sn=n2+3n+1呢? 设Sn是等差数列{an}的前n项和好,已知S6=36,Sn=324,S(n-6)=144,n>6,则n= 设Sn,Tn分别是两个等差数列{an}{bn}的前n项之和,若Sn/Tn=7n+1/4n+27,则an:bn=? 1.等差数列{an}中,a1*a7=16,则a4=2.等差数列{an}中,S12=72,那么a6+a7=3.自然数组成的一个数列,前n个偶数之和等于?4.已知等差数列{an}中,前n项之和为Sn,若S2n+1=(2n-1)(2n+1),则Sn等于?