`a)`
`4(3x-7) - 3 (2x+5) =9`
`=> 4 . 3x -4. 7 - 3 .2x - 3.5=9`
`=> 12x - 28 - 6x - 15=9`
`=> 12x-6x=9+28+15`
`=>6x=52`
`=>x=52:6`
`=>x=26/3`
Vậy `x=26/3`
`b)`
`2x (x-2) - (x+1)(2x-1) `
`= 2x . x - 2x . 2 - (2x . x - x . 1 + 1 . 2x - 1.1)`
`= 2x^2 - 4x - (2x^2 - x + 2x-1)`
` = 2x^2 - 4x - 2x^2 + x - 2x + 1`
`= (2x^2-2x^2) + (x-4x-2x)+1`
`= 1-5x`
---
`2x (x-2) = (x+1)(2x-1)`
` => 2x . x - 2x . 2 = x . 2x - x . 1 + 1 . 2x - 1 . 1`
`=> 2x^2 - 4x = 2x^2 - x + 2x - 1`
`=> 2x^2 - 4x - 2x^2 + x - 2x=-1`
`=> -5x=-1`
`=>x=1/5`
Vậy `x=1/5`
`c)`
`5 (x-3) + 4 (x+2) =12`
`=> 5 . x - 5 . 3 + 4 . x + 4 . 2 = 12`
`=> 5x-15+4x+8=12`
`=> 5x+4x=12+15-8`
`=>9x=19`
`=>x=19/9`
Vậy `x=19/9`
