Chapter 3 - Quadratic Functions - 3.1 Introduction to the Family of Quadratic Functions - Exercises and Problems for Section 3.1 - Skill Refresher - Page 120: S2

$A^4-2A^2B^2+B^4$

This expression can be rewritten as $$(A^2-B^2)(A^2-B^2)$$ Using the FOIL technique, the expression can be expanded as $$=A^2(A^2)-A^2(B^2)-A^2(B^2)+B^2(B^2)$$$$=A^4-2A^2B^2+B^4$$ (Note that $a^m(a^n)=a^{m+n}$.)