## Precalculus (6th Edition) Blitzer

$(x+2)(x-1)(x+1)$
Regroup to obtain: $=(x^3+2x^2) + (-x-2)$ Factor out $x^2$ in the first group and $-1$ in the second to obtain: $=x^2(x+2) + (-1)(x+2) \\=x^2(x+2) - 1(x+2)$ Factor out the GCF of $x+2$ to obtain: $=(x+2)(x^2-1) \\=(x+2)(x^2-1^2)$ Factor the difference of two squares using the formula $a^2-b^2=(a-b)(a+b)$ where $a=x$ and $b=1$ to obtain: $=(x+2)(x-1)(x+1)$