To expand a product of three factors, I can use the distributive property twice. First, I can multiply the two binomials $(x-2)(x+2)$ by applying the FOIL method. That gives me $x^2-4$. Then, I can multiply this by the third factor $(x^2+4)$ by distributing each term. That gives me $x^2(x^2+4) - 4(x^2+4)$. Simplifying this, I get $x^4+4x^2-4x^2-16$. Combining like terms, I get $x^4-16$. 
Expand $(x-2)(x+2)(x^2+4)$.