Đáp án:
`( x- 3) (x^2 +3x +9)-(x^2 +3)(x- 9)`
`=x^3-27-[x^3-9x^2+3x-27)`
`=x^3-27-x^3+9x^2-3x+27`
`=9x^2-3x`
`=3x(3x-1)`
tìm `x`
`(2x-3 )(3+2x)-x(x-1 )=3(x-1)^2`
`<=>(2x-3 )(3+2x)-x(x-1 )-3(x-1)^2=0`
`<=>4x^2-9-x^2+x-3(x^2-2x+1)=0`
`<=>4x^2-9-x^2+x-3x^2+6x-3=0`
`<=>-12+7x=0`
`<=>7x=0+12`
`<=>7x=12`
`<=>x=12/7`