tìm x biết a) (4-3x) (x+3)+(x-7) (3x-1) = 73 b) (4-5x) (3x-2) - (2-3x) (5x+1) = -40 [ chi tiết giúp tớ ạ , hứa vote 5 sao ]

`a, (4 - 3x)(x + 3) + (x - 7)(3x -1) = 73`

`<=> 4x +12 -3x^2 - 9x + 3x^2 -x -21x + 7 = 73`

`<=> -27x + 19 = 73`

`<=> -27x = 73 -19`

`<=> -27x = 54`

`<=> x =- 2`

Vậy `x =-2`

`b, (4 - 5x)(3x - 2) - (2 - 3x)(5x +1) = -40`

`<=> 12x - 8 -15^2 +10x - 10x - 2 + 15x^2 + 3x = -40`

`<=> 15x -10 = -40`

`<=>15x = -30`

`<=> x =-2`

Vậy `x = -2`

`@`Duongg7109612009