x^3+x^2-14x-8=x^3-16x+x^2+2x-8
=x(x^2-16x)+x^2+2x-8
=x(x+4)(x-4)+(x+4)(x-2)
=(x+4)[x(x-4)+x-2]
=(x+4)(x^2-3x-2)