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

Toán Lớp 6: 1) 1+(-4)+2+(-5)+ 3+(-6)+…+17+(-20) 2) 1-3+2-4+3-5+…+ 20–- 23

Toán Lớp 6: 1) 1+(-4)+2+(-5)+ 3+(-6)+…+17+(-20)
2) 1-3+2-4+3-5+…+ 20–- 23

Comments ( 2 )

  1. a, 1 + (-4) + 2 + (-5)+3+(-6) +…+ 17+(-20)
    = 1 – 4 + 2 – 5 + 3 – 6 +…+ 17 – 20
    = (1-4) + (2-5) +…+ (17 – 20)
    = (-3) + (-3) +…+ (-3)
    = (-3). 17
    = -51
    b, 1 – 3 + 2 – 4+ 3 – 5…+ 20 – 23
    = (1-3) + (2-4) + (3-5) ….+ (20 – 23)
    = (-2) + (-2) + (-2)+…+ (-3)
    = (-2). 20
    = -40
     

  2. 1)
    Ta có:
    1+(-4)+2+(-5)+3+(-6)+…+17+(-20)
    = 1-4+2-5+3-6+…+17-20
    = -3-3-3-…-3
    = 17(-3)
    = -51
     2)
    số các số hạng là:
    (23-1):1+1=23(số hạng)
    theo bài ra ta có:
    (1-3)+…+(20-23)=-2*11+1=-44

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