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

Toán Lớp 6: A=1-2+3-4+5-6+…+97-98+99-100 Giúp tôi với

Toán Lớp 6: A=1-2+3-4+5-6+…+97-98+99-100
Giúp tôi với

Comments ( 2 )

  1.  A = 1-2 + 3-4 + 5-6 + … + 97 – 98 + 99 – 100
    A = ( 1-2 ) + ( 3-4) + ( 5-6 ) + … + (97-98 ) + (99-100)
     Số cặp số -1 là :
      2 . 50 – 1 = 99 => Có 50 ( cặp )
     A = ( 1-2 ) + ( 3-4) + ( 5-6 ) + … + (97-98 ) + (99-100)
    => A = ( – 1) . 50
    => A = -50 

  2. A = 1 – 2 + 3 – 4 + 5 – 6 + … + 97 – 98 + 99 – 100
    A = (1 – 2) + (3 – 4) + (5 – 6) + … + (97 – 98) + (99 – 100)
    A = (-1) + (-1) + (-1) + … + (-1) + (-1) (Có: 100 : 2 = 50 số -1)
    A = (-1) . 50
    A = -50

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