Continuing with the lessons, we learned to factor difference of squares expressions. I used a geometric approach to help make sense out of the pattern, and it has really helped some students figure out how to more easily factor the nasty ones like 25x^2 - 16y^4. A quick sketch of the squares, labeled with their side lengths, has proven quite useful.
Lesson 9 (Difference of Squares) doc / keynote / quicktime
Lesson 10 (Review and Practice) doc / keynote / quicktime