3a85a15的知识精选

设等差数列{an}满足3a8=5a15,且a1>0,Sn为其前n项和,则数列{Sn}的最大项为(  )A...
问题详情:设等差数列{an}满足3a8=5a15,且a1>0,Sn为其前n项和,则数列{Sn}的最大项为()A.S23             B.S24         C.S25          D.S26【回答】C解析设等差数列{an}的公差为d,...
设等差数列{an}满足3a8=5a15,且,Sn为其前n项和,则数列{Sn}的最大项为(  )A.B.S24 ...
问题详情:设等差数列{an}满足3a8=5a15,且,Sn为其前n项和,则数列{Sn}的最大项为()A.B.S24  C.S25  D.S26【回答】C【考点】85:等差数列的前n项和.【分析】设等差数列{an}的公差为d,由3a8=5a15,利用通项公式化为2a1+49d=0,由,可得d<0...
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