Trang chủ » Hỏi đáp » Môn Toán /1/1.3+1/3.5+1/5.7+…+1/2009.2011 21/09/2023 /1/1.3+1/3.5+1/5.7+…+1/2009.2011
1/(1 . 3)+1/(3 . 5)+ 1/(5 . 7)+….+1/(2009 . 2011) =1/2 . (1/1-1/3)+1/2 . ( 1/3-1/5)+1/2 . (1/5-1/7)+……1/2 . ( 1/2009-1/2011) =1/2 . (1/1-1/3+1/3-1/5+1/5-1/7+…..1/2009-1/2011) =1/2 . (1/1-1/2011) =1/2 . 2010/2011 =1005/2011 Trả lời
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