Showing posts with label simplifying polynomials. Show all posts
Showing posts with label simplifying polynomials. Show all posts

Wednesday, February 24, 2010

Do you FOIL?

How do you teach your students to simplify (x+3)(x+4)? I used to tell them to use "FOIL," mainly because that's the way I learned it and that's the way the other teachers all taught it. The problem I have with FOIL is when they get to problems involving trinomials. If they've memorized the word FOIL, they have no idea what to do if there are extra terms.

Instead of using FOIL, I've found it works much better to start with simpler problems like (x)(x+4) - this way when you get to (x+3)(x+4), most students correctly suggest that you just need to distribute twice. First distribute the x, then distribute the 3. Why have them memorize FOIL when you could just show them that they're just distributing twice? I've found that my students have a much better understanding of the concept and will be able to tackle harder problems that have more terms.

I know there are other teachers still using FOIL, so I do tell them about it at some point, but most agree with me on the need for it.