Bài `4`
`a)(x+2)(x^2-2x+4)-x(x+3)(x-3)=26`
`⇔(x^3+8)-x(x^2-9)=26`
`⇔x^3+8-x^3+9x=26`
`⇔(x^3-x^3)+9x=26-8`
`⇔9x=18`
`⇔x=2`
Vậy `x=2`
`b)(x-3)(x^2+3x+9)-x(x-4)(x+4)=21`
`⇔(x^3-27)-x(x^2-16)=21`
`⇔x^3-27-x^3+16x=21`
`⇔(x^3-x^3)+16x=21+27`
`⇔16x=48`
`⇔x=3`
Vậy `x=3`
`c)(2x-1)(4x^2+2x+1)-4x(2x^2-3)=23`
`⇔(8x^3-1)-8x^3+12x=23`
`⇔8x^3-1-8x^3+12x=23`
`⇔(8x^3-8x^3)+12x=23+1`
`⇔12x=24`
`⇔x=2`
Vậy `x=2`
