等差数列{an}的公差不为零,首项a1=1,a2是a1和a5的等比中项,则数列{an}的前10项之和是 [ ]A.90 B.100
题型:吉林省模拟题难度:来源:
等差数列{an}的公差不为零,首项a1=1,a2是a1和a5的等比中项,则数列{an}的前10项之和是 |
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A.90 B.100 C.145 D.190 |
答案
B |
举一反三
已知等差数列{an}的前n项和为Sn,若m>1,且am﹣1+am+1﹣﹣1=0,S2m﹣1=39,则m等于 |
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A.39 B.20 C.19 D.10 |
等差数列{an}的前n项和为Sn,且S3=6,a1=4,则公差d等于( ). |
记等差数列{an}的前n项和为Sn,设S3=12,且2a1,a2,a3+1成等比数列,求Sn. |
数列{an}对任意n∈N*,满足a n+1=an+3,且a3=8,则S10等于 |
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A.155 B.160 C.172 D.240 |
设数列{an}(n∈N*)满足a n+2=2a n+1﹣an,Sn是其前n项的和,且S5<S6,S6=S7>S8,则下列结论错误的是 |
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A.a n+1﹣an<0 B.a7=0 C.S9>S5 D.S6与S7均为Sn的最大值 |
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