前n项和是Sn=n2+2n-1,则{an}为等差数列吗?为什么?
等差数列{An},{Bn}的前n项和为Sn与Tn,若Sn/Tn=2n/3n+1,则An/Bn的值是?
已知等差数列{an}的前n项和Sn满足:Sn=n2+2n+a(n∈N*),则实数a=______.
等差数列{An},{Bn}的前n项和为Sn与Tn,若Sn/Tn=2n/3n+1,则A5/B7的值是
已知数列{An}的前N项和Sn=4n2+3n,求证{An}是等差数列
等差数列{an}前n项和为Sn=3n-2n^2,求an
设数列an的前n项和为Sn,a1=1,an=(Sn/n)+2(n-1)(n∈N*) 求证:数列an为等差数列,
已知等差数列{an}的前n项和为Sn,且(2n-1)Sn+1 -(2n+1)Sn=4n²-1(n∈N*)
.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?
已知数列{an}中,a2=2,前n项和为Sn,且Sn=n(an+1)/2证明数列{an+1-an}是等差数列
已知等差数列{an}的前n项和是Sn=2n2-25n,试求数列{|an|}的前10项的和.
已知数列{an}的前n项和为Sn=n^2-3n,求证:数列{an}是等差数列
等差数列{An}的前n项和为Sn,若 lim Sn/n方 =2