Bài 1. (2 điểm) Tìm x biết: a) $−0, 1: x = -0,2 : 0,06$ b) $\frac{2-x}{4}$ $= \frac{3x-1}{3}$  c) $\frac{2x-1}{27}=$ $\frac{3}{2x-1}$ 

`\bb a)`

`-0,1 :x = -0,2 : 0,06`

`=> -0,1:x = -10/3`

`=> x = (-0,1) : (-10)/(3)`

`=> x = 0,03`

`\bb b)`

`(2-x)/(4) = (3x-1)/(3)`

`=> 3(2-x) = 4(3x-1)`

`=> 6-3x = 12x -4`

`=> -3x - 12x = -4-6`

`=>  -15x = -10`

`=> x = (-10)/(-15)`

`=> x = 2/3`

`\bb c)`

`(2x-1)/(27) = (3)/(2x-1)`

`=> (2x-1)(2x-1) = 27.3`

`=> (2x-1)^2 = 81`

`=> (2x-1)^2 = (+-9)^2`

TH1:

`2x-1 = 9`

`=> 2x = 9+1`

`=> 2x = 10`

`=> x = 10:2`

`=> x = 5`

TH2:

`2x-1 = -9`

`=> 2x = -9+1`

`=> 2x =-8`

`=> x = (-8):2`

`=> x = -4`

Vậy `x in {5;-4}`