(x-2) * x = (x-1) * (x+4)

Đáp án:

`(x-  2).x = (x - 1).(x + 4)`

`-> x.x - 2.x = x.(x + 4) - (x + 4)`

`-> x^2 - 2x = x.x + 4.x  - x - 4`

`-> x^2 - 2x = x^2 + 4x  - x - 4`

`-> x^2 - x^2 - 2x - 4x + x = -4`

`-> -5x = -4`

`-> x = 4/5`

Vậy `x = 4/5`

$#dariana$

`( x - 2 ) . x = ( x - 1 ) . ( x + 4 )`

`⇒ x . x - 2 . x = x . ( x + 4 ) - 1 . ( x + 4 )`

`⇒ x^2 - 2x = x^2 + 4x - x - 4`

`⇒ x^2 - 2x - x^2 - 4x + x = - 4`

`⇒ ( x^2 - x^2 ) - ( 2x + 4x - x ) = - 4`

`⇒ 0 - 5x = - 4`

`⇒ - 5x = - 4`

`⇒ x = ( - 4 ) : ( - 5 )`

`⇒ x = 4/5`

Vậy `, x = 4/5 .`