f(x) = 3x^3 + 14x^2 - 23x + 6
If -6 is a zero of f(x), then we can write, x = -6, or equivalently, (x + 6) = 0.
This means (x + 6) is a factor of f(x), so we can take out that factor by dividing f(x) by (x + 6).
(x+6)(3x^2 - 4x + 1) --- now factorise the quadratic
(x+6)(3x-1)(x-1)