a9a10a11的知识精选

已知{an}是等差数列,a7+a13=20,则a9+a10+a11= (  )A.36          B....
问题详情:已知{an}是等差数列,a7+a13=20,则a9+a10+a11= (  )A.36          B.30        C.24            D.18【回答】B;知识点:数列题型:选择题...
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