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

Toán Lớp 6: 1.Tính bằng cách thuận tiện: a) 29 x (19 – 13) – 19 x (29 – 13) b) (-12) x 47 + (-12) x 52 + (-12) c) 31 x (-18) + 31 x (-81

Toán Lớp 6: 1.Tính bằng cách thuận tiện:
a) 29 x (19 – 13) – 19 x (29 – 13)
b) (-12) x 47 + (-12) x 52 + (-12)
c) 31 x (-18) + 31 x (-81) – 31
d) (4200 – 378) : 21

Comments ( 2 )

  1. Lời giải chi tiết:
    a) 29xx(19-13)-19xx(29-13)
    =29xx19-29xx13-19xx29+19xx13
    =(29xx19-19xx29)-(29xx13-19xx13)
    =19xx(29-29)-13xx(29-19)
    =19xx0-13xx10
    =0-130
    =-130
    b) (-12)xx47+(-12)xx52+(-12)
    =-12.(47+52+1)
    =-12.100
    =-1200
    c) 31xx(-18)+31xx(-81)-31
    =31xx(-18)+31xx(-81)+31xx(-1)
    =31xx[(-18)+(-81)+(-1)]
    =31xx(-100)
    =-3100
    d) (4200-378):21
    =4200:21-378:21
    =200-18
    =182

  2. a) 29 . (19 – 13) – 19 . (29 – 13)
    = 29 . 19 – 29 . 13 – 19 . 29 – 19 . 13
    = (29 . 19 – 19 . 29) – (29 . 13 – 19 . 13)
    = 0 – 13 . (29 – 19)
    = 0 – 13 . 10
    = 0 – 130
    = -130
    b) (-12) . 47 + (-12) . 52 + (-12)
    = (-12) . (47 + 52 + 1)
    = (-12) . 100
    = -1200
    c) 31 . (-18) + 31 . (-81) – 31
    = 31 . [(-18) + (-81) – 1]
    = 31 . (-100)
    = -3100
    c) (4200 – 378) : 21
    = 4200 : 21 – 378 : 21
    = 200 – 18
    = 182

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