Tìm x: a) -1,75x + 3$\frac{3}{4}$x = -24 b) 2( x + $\frac{1}{2}$ ) = 4x - 5 c) $\frac{-4}{7}$ = $\frac{x - 40}{31 - 5x}$

1 câu trả lời

`a) -1,75x + 3,75x = -24`

`<=> x (-1,75 + 3,75) =-24`

`<=>2x= -24`

`<=> x = -12`

`b) 2(x+1/2) = 4x-5`

`<=> 2x + 1 = 4x -5`

`<=> 2x-4x = -5-1`

`<=> -2x = -6`

`<=> x =3`

`c) -4/7 = (x-40)/(31-5x)`

`=> -4.(31-5x) = 7.(x-40)`

`<=> -124 + 20x = 7x -280`

`<=> 13x =-156`

`<=> x = -12`