Precalculus (6th Edition) Blitzer

$(x-3)(x^2+4)$
Regroup to obtain $(x^3-3x^2)+(4x-12)$. Factor out $x^2$ in the first group and $4$ in the second: $x^2(x-3)+4(x-3)$. Factor out $(x-3)$ to obtain $(x-3)(x^2+4)$.