Answer
`x^3 - 5x^2 + 2x + 8`
`= x^3 - x^2 - 4x^2 - 2x + 4x + 8`
`= (x^3 - x^2 - 2x) - (4x^2 - 4x - 8)`
`= x . (x^2 - x - 2) - 4 . (x^2 - x - 2)`
`= (x - 4) . (x^2 - x - 2)`
`= (x - 4) . (x^2 - 2x + x - 2)`
`= (x - 4) . [(x^2 - 2x) + (x - 2)]`
`= (x - 4) . [x . (x - 2) + (x - 2) . 1]`
`= (x - 4) . (x + 1) . (x - 2)`