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

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−4x+53x−6−12=2x−32x−4

<=> x+53(x−2)−12=2x−32(x−3)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}