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

Toán Lớp 6: Thực hiện phép tính(tính hợp lý nếu có thể) a, 7-8+9-10+11-12+…+2009-2010 b, (1456+23)-1456 c, (-1999)-(-234-1999) d, (116+124)-(215-

Toán Lớp 6: Thực hiện phép tính(tính hợp lý nếu có thể)
a, 7-8+9-10+11-12+…+2009-2010
b, (1456+23)-1456
c, (-1999)-(-234-1999)
d, (116+124)-(215-116-124)

Comments ( 2 )

  1. a)A = 7 – 8 + 9 – 10 + 11 – 12 + …… + 2009 – 2010 ( có ( 2010 – 7 ) : 1 + 1 = 2004 số)
    = ( 7 – 8 ) + ( 9 – 10 ) + ( 11 – 12 ) + …… + ( 2009 – 2010 ) (có 1002 cặp)
    = ( – 1 ) + ( – 1 ) + ( – 1 ) + …… + ( – 1 )
    =-1.1002
    -1002
    b)(1456+23)-1456
    =1456+23-1456
    =(1456-1456)+23
    =23
    c)(-1999)-(-234-1999)
    =-1999+234+1999
    =(-1999+1999)+234
    =234
    d)(116+124)-(215-116-124)
    =116+124-215+116+124
    =(116+116)+(124+124)-215
    =265

  2. a)
    7-8+9-10+11-12+…+2009-2010
    =(7-8)+(9-10)+(11-12)+…+(2009-2010)
    =(-1)+(-1)+(-1)+…+(-1) ( có 1002 chữ số)
    =(-1).1002
    =-1002
    $\\$
    b)
    (1456+23)-1456
    =1456+23-1456
    =(1456-1456)+23
    =0+23
    =23
    $\\$
    c)
    (-1999)-(-234-1999)
    =(-1999)+234+1999
    =[(-1999)+1999]+234
    =0+234
    =234
    $\\$
    d
    (116+124)-(215-116-124)
    =116+124-215+116+124
    =(116+116)+(124+124)-215
    =232+248-215
    =480-215
    =265
     

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

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