You want the roots or the zeros?
x^3-4x^2+x+6
x^3+x-4x^2+6
x^3+x-(4x^2-6)
x^3+x-2(2x^2-3)
No, this did not help.
Look at Rational Roots Theorem.
Try -2 and +2.
2 | 1 -4 1 6
|
| 2 -4 -6
|-------------------------
1 -2 -3 0
The result means one factor is and other factor
which is composed of and .
Your factorization is .
(testing for -2 did not give a zero remainder.)