设Sn是等差数列an的前n项和,S9= -26,S13= -144,等比数列bn中,b5=a5,b7=a7则b6等于
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设sn是等差数列{an}的前n项和, 若a5:a7=2:3,求s9:(s13-s9)
设Sn是等差数列{an}的前n项和,a12=-8,S9=-9.则S16=?
设Sn是等差数列an的前n项和,a5=5a3,则S9/S5=?
设Sn是等差数列an的前n项和,若a5/a3=5/9,则S9/S5=
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设Sn是等差数列an的前n项和,若S5/S3=5/9,则S9/S5=
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设Sn是等比数列{an}的前n项和,S3,S9,S6,成等差数列,则公比q=?
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设等差数列{AN}的前N项和为SN,若S9>0,S10
设等差数列 {an}的前n 项和为Sn,若S9>0 ,S10
设Sn是等差数列{an}的前n项和,a12=-8,S9=-9,﹛Sn/n﹜是等差数列,求﹛Sn/n﹜的前n项的和
设Sn为等差数列an的前n项和,S4=14,S10-S7=30,则S9=
设等差数列an的前n项和为Sn,若S6=24,S9=63,则S15=
设sn为等差数列(an)的前n项和,s4=14,s10-s7=30.则s9...