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

Toán Lớp 6: Câu 8: a) Tính: S = -57 – (98 – 57) + (98 – 42) b) P = 5 – 6 + 7 – 8 +…+ 99 -100

Toán Lớp 6: Câu 8:
a) Tính: S = -57 – (98 – 57) + (98 – 42)
b) P = 5 – 6 + 7 – 8 +…+ 99 -100

Comments ( 2 )

  1. Lời giải chi tiết:
    a) S=-57-(98-57)+(98-42)
    S=-57-98+57+98-42
    S=(-57+57)+(98-98)-42
    S=0+0-42
    S=-42
    b) P=5-6+7-8+…+99-100
    P=(5-6)+(7-8)+…+(99-100)
    P=\underbrace{-1+(-1)+…+(-1)}_{\text{48 số hạng -1}}
    P=-1.48
    P=-48

  2. a) -57 – ( 98 – 57 ) + ( 98 – 42 )
    = -57 – 98 + 57 + 98 – 42
    = (-57 + 57) + (-98 + 98) – 42
    = 0 + 0 – 42
    = -42
    b) 5 – 6 + 7 – 8 + … + 99 – 100
    = ( 5 – 6 ) + ( 7 – 8 ) + … + ( 99 – 100 )
    = -1 + (-1) + (-1) + … + (-1)
    = -1 . 48
    = -48
     

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