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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 6: Tính tổng sau : S=1-2+3-4+–…+2005-2006

Toán Lớp 6: Tính tổng sau :
S=1-2+3-4+………..+2005-2006

Comments ( 2 )

  1. Answer
    S = 1 – 2 + 3 – 4 + … + 2005 – 2006
    S = (1 – 2) + (3 – 4) + … + (2005 – 2006)
    S = \underbrace{-1 – 1 – … – 1}_{\text{có 1003 cặp}}
    S = -1 . 1003
    S = -1003

  2. S=1-2+3-4+…+2005-2006
    = (1-2) + (3-4) +…+(2005-2006)
    =-1+ (-1) + …+ (-1)
    Dãy số trên có : [($2006-1$) : $1 + 1$] : $2 =1003$ ( cặp số )
    S= -1.1003
    S=-1003

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222-9+11+12:2*14+14 = ? ( )

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