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

Toán Lớp 7: a) |3/2x + 1/2| = |4x – 1| b) |5/4x – 7/2| – |5/8x + 3/5| = 0 c) |7/5x + 2/3| = |4/3x – 1/4| d) |7/8x + 5/6| – |1/2x + 5| = 0

Toán Lớp 7: a) |3/2x + 1/2| = |4x – 1|
b) |5/4x – 7/2| – |5/8x + 3/5| = 0
c) |7/5x + 2/3| = |4/3x – 1/4|
d) |7/8x + 5/6| – |1/2x + 5| = 0

Comments ( 1 )

  1. Giải đáp:
    $\\$
    a,
    |3/2x + 1/2| = |4x-1|
    Trường hợp 1 :
    ↔ 3/2x + 1/2 = 4x-1
    ↔ 3/2x – 4x=  -1/2 – 1
    ↔ (-5)/2x = (-3)/2
    ↔x=(-3)/2 ÷ (-5)/2
    ↔x=3/5
    Trường hợp 2 :
    ↔ 3/2x + 1/2 = – (4x-1)
    ↔ 3/2x + 1/2 = -4x + 1
    ↔ 3/2x + 4x = -1/2 +1
    ↔ 11/2x = 1/2
    ↔x=1/2 ÷ 11/2
    ↔x=1/11
    Vậy x ∈ {3/5; 1/11}
    $\\$
    b,
    |5/4x – 7/2|  – |5/8x + 3/5| = 0
    ↔ |5/4x – 7/2| = 0 + |5/8x + 3/5|
    ↔ |5/4x – 7/2| = |5/8x + 3/5|
    Trường hợp 1 :
    ↔ 5/4x – 7/2 = 5/8x + 3/5
    ↔ 5/4x – 5/8x = 7/2 + 3/5
    ↔ 5/8x = 41/10
    ↔x=41/10 ÷ 5/8
    ↔x=164/25
    Trường hợp 2 :
    ↔5/4x – 7/2 = – (5/8x + 3/5)
    ↔ 5/4x – 7/2 = -5/8x – 3/5
    ↔ 5/4x + 5/8x = 7/2 – 3/5
    ↔ 15/8x  = 29/10
    ↔x=29/10 ÷ 15/8
    ↔x=116/75
    Vậy x ∈ {164/25; 116/75}
    $\\$
    c,
    |7/5x  + 2/3| = |4/3x – 1/4|
    Trường hợp 1 :
    ↔ 7/5x + 2/3 = 4/3x – 1/4
    ↔ 7/5x – 4/3x = -2/3 – 1/4
    ↔ 1/15x = (-11)/12
    ↔x=(-11)/12 ÷ 1/15
    ↔x=(-55)/4
    Trường hợp 2 :
    ↔ 7/5x + 2/3 = – (4/3x – 1/4)
    ↔ 7/5x + 2/3 = -4/3x  + 1/4
    ↔ 7/5x + 4/3x = -2/3 + 1/4
    ↔ 41/15x = (-5)/12
    ↔x=(-5)/12 ÷ 41/15
    ↔x=(-25)/164
    Vậy x ∈ { (-55)/4; (-25)/164}
    $\\$
    d,
    |7/8x + 5/6| – |1/2x + 5| = 0
    ↔ |7/8x + 5/6| = 0 + |1/2x + 5|
    ↔ |7/8x + 5/6| = |1/2x + 5|
    Trường hợp 1 :
    ↔ 7/8x + 5/6 = 1/2x + 5
    ↔ 7/8x – 1/2x = -5/6 + 5
    ↔ 3/8x  =25/6
    ↔x=25/6÷3/8
    ↔x=100/9
    Trường hợp 2 :
    ↔ 7/8x + 5/6 = – (1/2x + 5)
    ↔ 7/8x + 5/6 = -1/2x  – 5
    ↔ 7/8x + 1/2x = -5/6 – 5
    ↔ 11/8x  = (-35)/6
    ↔x=(-35)/6 ÷ 11/8
    ↔x=(-140)/33
    Vậy x ∈ {100/9; (-140)/33}

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