Intermediate Algebra for College Students (7th Edition)

$(x+3)(x+2)(x-2)$
The product of a binomial sum and a binomial difference is: $(A+B)(A-B)=A^2-B^2$. Hence here: $x^3+3x^2-4x-12=x^2(x+3)-4(x+3)=(x+3)(x^2-4)=(x+3)(x^2-2^2)=(x+3)(x+2)(x-2)$