等差数列{an}的前n项和为sn,且a5+a6=3,则s11=

等差数列an的前n项和为Sn,且a5+a21=a12,求S27 设等差数列｛An｝的前n项和为Sn,且A5＝5A3,则S9/S5＝? 设等差数列{an}的前N项和为Sn,且a3+a5+a7=15,则S9=? 等差数列{an}的前n项和为sn,且a5+a6=3,则s11= 设等差数列{an}的前n项和为Sn,且a5=3a7,则S9/S13=? 已知等差数列{an}的前n项和为sn,且a5=15,s15>0,s16 等差数列an中,a50,且a6>/a5/,sn为数列an的前n项和,则使sn>0的n的最小值是 等差数列an和bn的前n项和分别为sn和tn,且sn/tn=2n/3n+1,则a5/b5=? 等差数列{an}和{bn}的前n项和分解为Sn和Tn,且Sn/Tn=2n/(3n+1),则a5/b5=? 已知{an}{bn}都为等差数列,前n项的和分别为Sn,Tn,且Sn/Tn=5n/6n+1,求a5/b5. 等差数列{an},{bn}的前n项和分别为Sn,Tn,且Sn/Tn=(2n-1)/(3n+2),则a5/b5 在等差数列｛an}中,a5+a10=0,且a10大于a5,则使数列前N项和为Sn取的最小值的n等于? ｛an｝为等差数列,前n项和为Sn,且a1+a3+a5=105.a2+a4+a6=99 使Sn达到最大值的n是多少 ｛an｝为等差数列,前n项和为Sn,且a1+a3+a5=105.a2+a4+a6=99 使Sn达到最大值的n是多少 等差数列an中,公差d>0,且a5+a10=0,记数列-2/an的前n项和为Sn,则使Sn 等差数列an的前n项和为Sn,已知a5=11 a8=5求an和Sn 数列an是等差数列,a1>0,且|a5|=|a9|,则an的前n项和为Sn,取最大时,n=? 等差数列(an)为递增数列,前n项和为sn,且a1,a3,a9,成等比数列s5=(a5)的平方,问An