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

A beautiful combinatorics argument

11 hours ago

## 3 comments:

If you take the leftover pink L shape, cut it at the diagonal and rearrange the two trapezoidal shapes into a rectangle, you will create a rectangle with dimensions of (x-2) and (x+2)... Just thought I'd through that out there for next year :)

So how does Tic-Tac Toe Battle Royal work?

Thanks, MizT. That's cool - I never saw that one before.

MrSnyder, I wrote about Tic Tac Toe in an earlier post. Here is the link.

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