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∵{an}是等差数列,∴s5=a1+a2+…+a5=5a3,a2+a8=2a5, 又S5=3(a2+a8), ∴5a3=3×2a5, ∴ a5 a3= 5 6 故答案为 5 6
设Sn是等差数列{an}的前n项和,S5=3(a2+a8),则a5a3的值为 ___ .
设Sn是等差数列{an}的前n项和,若a5a3=59,则S9S5=( )
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.
设等差数列{an}的前n项和为Sn,若S3=9,S5=20,则a7+a8+a9=( )
设等差数列{an}的前n项和为Sn,已知a2=3,S5=25
设Sn是等差数列{an}的前n项和,若S5=a8+5,S6=a7+a9-5,则公差d等于______.
设数列{an}是等差数列,a2=-6,a8=6,Sn是数列{an}的前n项和,则( )
设等差数列an的前n项和为Sn,若S4>=10,S5
已知等差数列{an}的前n项和为Sn,且a2=-5,S5=-20.
设Sn为等差数列{an}的前n项和,若S15=90,则a8等于( )
设Sn是等差数列{an}(n∈N+)的前n项和,且a1=1,a4=7,则S5=______.
设数列{an}为等差数列,前n项和为Sn,已知a2=2,S5=15,求{an}的通项公式
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