`d)` `(x+2)(x^2 - 2x+4) - (x^2+3)x = 14`

`x . x^2 - 2x . x + 4 . x + 2 . x^2 - 2 . 2x + 2 . 4 - x^2 . x - 3 . x = 14`

`x^3 - 2x^2 + 4x + 2x^2 -4x + 8 - x^3 - 3x=14`

`(x^3 - x^3) - (2x^2+2x^2) - (3x +4x-4x) + 8 =14`

`0  - 0 - 3x + 8 =14`

`-3x = 14-8`

`-3x = 6`

`x = 6:(-3)`

`x=-2`

Vậy `x=-2`

`e)` `(x-2)(x^2 +2x+4) - x(x^2 - 2) =8`

`x . x^2 + 2x . x + 4 . x - 2 . x^2 - 2 . 2x - 2 . 4 - x . x^2 + x . 2 =8`

`x^3 + 2x^2 + 4x - 2x^2 - 4x - 8 - x^3 + 2x = 8`

`(x^3 - x^3) + (2x^2 - 2x^2) + (2x+ 4x-4x) -8  =8`

`0 + 0 +2x - 8=8`

`2x=16`

`x=16:2`

`x=8`

Vậy `x=8`