bài 2: giải các pt sau a, 5x-4/2=16+1/7 b, 3(x-11)/4=3(x+1)/5-2(2x-5)/10 c, x+2/3 + 3(2x-1)/4-5x-3/6= x+5/12 d, 1/2(x+1) + 1/4(x+3)=3-1/3(x+2) bài 4:

bài 2: giải các pt sau
a, 5x-4/2=16+1/7
b, 3(x-11)/4=3(x+1)/5-2(2x-5)/10
c, x+2/3 + 3(2x-1)/4-5x-3/6= x+5/12
d, 1/2(x+1) + 1/4(x+3)=3-1/3(x+2)
bài 4: giải các phương trình sau
a, x+5/3x-6 – 1/2 =2x-3/2x-4
b, 3/2x-16 + 3x-20/x-8 + 1/8=13x-102/3x-24
c, 1/x+1 – 5/x-2= 15/(x+1) (2-x)
d, 12/1-9x^2= 1-3x/1+3x – 1+3x/1-3x
e, x+1/x-2 – 5/x+2=12/x^2-4+1
f, 2x+1/2x-1 – 2x-1/2x+1= 8/4x^2-1

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  1. 2.

    a) (5x – 4)/2 = (16x + 1)/7
    <=> 7(5x-4)/14 = 2(16x+1)/14
    <=> 7(5x-4)       = 2(16x+1)
    <=> 35x – 28      = 32x + 2
    <=>    35x – 32x   = 2 + 28
    <=>          3x         = 30
    <=>            x           = 10
    Vậy S = { 10}

    b)3(x-11)/4 = 3(x+1)/5 – 2(2x-5)/10
    <=> 15(x-11)/20 = 12(x+1)/20 – 4(2x-5)/20
    <=> 15(x-11)       = 12(x+1) – 4(2x-5)
    <=>  15x – 165     = 12x + 12 – 8x + 20
    <=>   15x + 8x     = 12 + 20 – 165
    <=>       23x         = – 132
    <=>           x          = -109
    Vậy S = { -109}

    c)  x + 2/3 + 3 (2x-1)/4 – 5x-3/6 = x + 5/12
    <=> 12x/12 + 8/12 + 9(2x-1)/12 – 2(5x-3)/12 = 12x/12 + 5/12
    <=> 12x + 8 + 9(2x-1) – 2(5x-3) = 12x + 5
    <=>  12x + 8 + 18x – 9 – 10x + 6 = 12x + 5
    <=> 12x – 12x + 18x – 10x = 5 -6 – 8 + 9 – 6
    <=>  8x   = -6
    <=>   x     = -6/8 = -3/4
    Vậy S = { -3/4}

    d) (1/2)(x+1) + (1/4)(x+3) = 3 – (1/3)(x+2)
    <=> x+1/2 + x+3 / 4 = 3 – x+2 / 3
    <=> 6(x+1)/12 + 3(x+3)/12 = 42/12 – 4(x+2)/12
    <=> 6(x+1) + 3(x+3)    = 42 – 4(x+2)
    <=>  6x + 6 + 3x + 9 = 42 – 4x -8
    <=>    9x + 4x = -8 – 15
    <=>        13x   = -23
    <=>            x    = -23/13
    Vậy S = { -23/13}

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  2. Đáp án:

    2.

    a) (5x – 4)/2 = (16x + 1)/7
    <=> 7(5x-4)/14 = 2(16x+1)/14
    <=> 7(5x-4)       = 2(16x+1)
    <=> 35x – 28      = 32x + 2
    <=>    35x – 32x   = 2 + 28
    <=>          3x         = 30
    <=>            x           = 10
    Vậy S = { 10}

    b)3(x-11)/4 = 3(x+1)/5 – 2(2x-5)/10
    <=> 15(x-11)/20 = 12(x+1)/20 – 4(2x-5)/20
    <=> 15(x-11)       = 12(x+1) – 4(2x-5)
    <=>  15x – 165     = 12x + 12 – 8x + 20
    <=>   15x + 8x     = 12 + 20 – 165
    <=>       23x         = – 132
    <=>           x          = -109
    Vậy S = { -109}

    c)  x + 2/3 + 3 (2x-1)/4 – 5x-3/6 = x + 5/12
    <=> 12x/12 + 8/12 + 9(2x-1)/12 – 2(5x-3)/12 = 12x/12 + 5/12
    <=> 12x + 8 + 9(2x-1) – 2(5x-3) = 12x + 5
    <=>  12x + 8 + 18x – 9 – 10x + 6 = 12x + 5
    <=> 12x – 12x + 18x – 10x = 5 -6 – 8 + 9 – 6
    <=>  8x   = -6
    <=>   x     = -6/8 = -3/4
    Vậy S = { -3/4}

    d) (1/2)(x+1) + (1/4)(x+3) = 3 – (1/3)(x+2)
    <=> x+1/2 + x+3 / 4 = 3 – x+2 / 3
    <=> 6(x+1)/12 + 3(x+3)/12 = 42/12 – 4(x+2)/12
    <=> 6(x+1) + 3(x+3)    = 42 – 4(x+2)
    <=>  6x + 6 + 3x + 9 = 42 – 4x -8
    <=>    9x + 4x = -8 – 15
    <=>        13x   = -23
    <=>            x    = -23/13
    Vậy S = { -23/13}

     4.

    a)x+53x−6−12=2x−32x−4

    <=> x+53(x−2)−12=2x−32(x−3)

    <=> 2(x + 5) – 3(x – 2) = 3(2x – 3)

    <=> 2x + 10 – 3x + 6 = 6x – 9

    <=> -x + 16 = 6x – 9

    <=> -x = 6x – 9 – 16

    <=> -x = 6x – 25

    <=> -x – 6x = -25

    <=> -7x = -25

    <=> x = 25/7
    Vậy S={25/7}

    b) 3/2x-16 + 3x-20/x-8 + 1/8=13x-102/3x-24 ( ĐKXĐ : x khác 8 )
    <=>  3/2x-16 + 3x-20/x-8 – 13x-102/3x-24 = – 1/8
    <=> 3/ 2(x – 8) + 3x – 20/ x – 8 – 13x – 102/ 3(x – 8) = – 1/8
    <=> 9 + 6( 3x – 20) – 2(13x – 102)/ 6( x – 8) = – 1/8
    <=> 93 – 8x / 6 ( x- 8) = – 1/8
    <=> 8 ( 93 – 8x) = -6 ( x – 8) 
    <=> 744 – 64x = -6x + 48
    <=> – 64x + 6x = 48 – 744
    <=> – 58x = -696
    <=> x = 12 ( TM)
    Vậy S = {12}
    c)ĐKXĐ: x khác -1 và 2
      Ta có:
           1/(x+1) -5/(x-2) = 15/(x+1)(x-2)
    <=> x-2 – 5(x+1) = 15
    <=> x = -11/2 (TM ĐKXĐ)
    Vậy S={-11/2}

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