Appendix A - Review - A.3 Polynomials - A.3 Assess Your Understanding - Page A29: 2

$x^{4}-16$

This is a difference of squares, $(A-B)(A+B)=A^{2}-B^{2}$. $(x^{2}-4)(x^{2}+4)=(x^{2})^{2}-4^{2}=x^{4}-16$ Note: FOIL can also be used, $(x^{2}-4)(x^{2}+4)\\ =x^{2}\cdot x^{2}+x^{2}\cdot 4-4x^{2}-16\\ =x^{4}-16$