I factored this at your other post,How do i factorize this?
. . but here's how I did it.
Knowing the Rational Roots Theorem,
. . I knew that the only rational roots are: .
From the Remainder Theorem, I knew that is a factor.
Using long division: .
I saw that is a root of the cubic.
. . Hence, is a factor.
And we have: .
The quadratic does not factor; use the Quadratic Formula.