I think we all know by now that teaching your students the old FOIL method for multiplying Binomials is a HUGE mistake!
When you do this you are teaching them to memorize a pattern that won’t apply anywhere else when they move beyond Binomials. The majority of the lessons involving polynomials after this lesson will involve distributing different monomials, binomials, tri-nomials, and so on… So, why teach them something they can’t actually use beyond that lesson?
That’s enough on why NOT to teach the FOIL method! You can however teach them this method without using the FOIL acronym making sure they understand everything in the first set of parenthesis gets distributed to every term in the second set of parenthesis. NO MATTER HOW MANY TERMS THERE ARE!
Here are 3 great ways to teach Multiplying Binomials and Beyond!
- It is all about distributing and in math, just like everywhere else, we like things distributed evenly. Check out our lesson on Algebra 1 Coach about Teaching Distributing with Cup Cakes! It can be found here: https://algebra1coach.com/the-distributive-property/
- Teach them that the Prefix Bi means 2. Which means they will be Distributing 2 monomials. The word distribute is the most important word. They need to relate distribute to multiply so when you move on to trinomials they know to Distribute 3 monomials because the prefix Tri means 3. You get the point…
- Do a refresher lesson on what separates terms in a math phrase. Recover with them that + and – signs separate terms and that they need to distribute each of the terms in the first set of parenthesis to each of the terms in the second set of parenthesis. Reminding them to check and make sure each of the terms in the second set of parenthesis received each of the terms in the first set of parenthesis. Again, because we all love when things are passed out evenly!
Remember, the most common mistakes students make when Multiplying Binomials, Trinomials, or more is that they do not distribute to all of the terms evenly. Leaving one term out is the most common mistake!
Below is a Great Video Reviewing the Multiple Methods to Multiply Binomials
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