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

Toán Lớp 6: A,4 1/2.(2,5-3 3/4)+(-1/2) B,-0,6.x-7/3=5,4 C,2,8:(1/5-3.x)=1 2/5

Toán Lớp 6: A,4 1/2.(2,5-3 3/4)+(-1/2) B,-0,6.x-7/3=5,4 C,2,8:(1/5-3.x)=1 2/5

Comments ( 2 )

  1. a) 4 1/2 . (2,5 – 3 3/4) + (-1/2)
    = 9/2 . ( 5/2 – 15/4) – 1/2
    = 9/2 . (-5/4) – 1/2
    = -45/8 – 1/2
    = -49/8
    $\\$
    b) -0,6 . x – 7/3 = 5,4
     -3/5 . x             = 27/5 + 7/3
    -3/5 . x               = 116/15
             x                 = 116/15 : (-3/5)
           x                  = -116/9
    Vậy x = -116/9
    $\\$
    c) 2,8 : (1/5 – 3x) = 1 2/5
     14/5 : (1/5 -3x) = 7/5
              (1/5 – 3x) = 14/5 : 7/5
               1/5 – 3x = 2
                        3x = 1/5 – 2
                         3x = -9/5
                           x = -9/5 : 3
                        x   = -3/5
    Vậy x = -3/5

  2. a, 4 1/2 . ( 2,5 – 3 3/4 ) + ( – 1 )/2
    = 9/2 . ( 5/2 – 15/4 ) + ( – 1 )/2
    = 9/2 . ( – 5 )/4 + ( – 1 )/2
    = ( – 45 )/8 + ( – 1 )/2
    = ( – 49 )/8
    b, – 0,6 . x – 7/3 = 5,4
    ⇔ ( – 3 )/5 . x – 7/3 = 27/5
    ⇔ ( – 3 )/5 . x = 27/5 + 7/3
    ⇔ ( – 3 )/5 . x = 116/15
    ⇔ x = 116/15 : ( – 3 )/5
    ⇔ x = ( – 116 )/9
    Vậy , x = ( – 116 )/9 .
    c, 2,8 : ( 1/5 – 3 . x ) = 1 2/5
    ⇔ 14/5 : ( 1/5 – 3 . x ) = 7/5
    ⇔ 1/5 – 3x = 14/5 : 7/5
    ⇔ 1/5 – 3x = 2
    ⇔ 3x = 1/5 – 2
    ⇔ 3x = ( – 9 )/5
    ⇔ x = ( – 9 )/5 : 3
    ⇔ x = ( – 3 )/5
    Vậy , x = ( – 3 )/5 .

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