a
设等差数列{an}的首项为a1,由等差数列的性质可得 a1+a9=2a5,a1+a5=2a3, ∴ s9 s5=
a1+a9 2×9
a1+a5 2×5= 9a5 5a3= 9 5× 5 9=1, 故选A.
设Sn是等差数列{an}的前n项和,若a5a3=59,则S9S5=( )
设等差数列{an}的前n项和为Sn.若a5=5a3,则S9S5=( )
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设Sn为等差数列{an}的前n项和,若a1=1,公差d=2,Sn+2-Sn=36,则n=( )
设Sn是等差数列{an}的前n项和,若S7=35,则a4=______.
设Sn是等差数列[an}的前n项和,若S7=5,则a4=
设Sn是等差数列{an}的前n项和,若a5/a3=5/9,则S9/S5=:
设Sn是等差数列An的前n项和,若S3/S6=1/3,则S6/S12等于
设Sn、Tn分别是等差数列an、bn的前n项和,Sn/Tn=(7n+2)/(n+3),则a6/b5=?
设等差数列{an}的前n项和为Sn,若存在正整数m,n(m<n),使得Sm=Sn,则Sm+n=0
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