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Counts on fingers & toes
Posts: 2
| I just wondering how many teachers teach this method in addition to Foil. Also, how they do so and not confuse students. I have always used this method (that was the way I was taught) and find it more straightforward than foil (distributative property). I like using because it is very similar to solving two step equations and students often catch on faster than using foil.
for example:
x + 5
2x + 4
_____________
4x + 20
2x^2 + 10x
______________
2x^2 + 14x + 20
Foil would be
(x)(2x) + (x)(4) + (2x)(5) + 4(5)
2x^2 + 4x + 10x + 20
2x^2 + 14x + 20
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Counts on fingers & toes
Posts: 3
| I taught my students to use the vertical method. That helps them do a better job at combining like terms. |
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Math
Posts: 9
Location: SCAPA | I truly have no preference. As a result, I chose to demo. each method. My students said they prefered the FOIL method. Only 2-3 students in the entire class preferred the vertical method. I also felt that the FOIL method lead in nicely to Chapter 5 - factoring polynomials. Just a personal preference. |
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Math
Posts: 24
Location: LTMS | The "box method" for multiplying whole numbers (the one where students draw the diagonal lines inside the boxes, etc.) also works for polynomials.
After all, multiplying polynomials is the same procedure as multiplying whole numbers; instead of using base 10, polynomials use base X.
So any method for multiplying whole numbers (that is based on place value) will have an analog with polynomials. For students who truly understand WHY a particular multiplication algorithm works, applying the method to polynomials is straightforward. For students who can do an algorithm, without understanding why it works, extending to algebra is difficult, at best. |
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Counts on fingers & toes
Posts: 11
| My students seemed to like foil better. I was surprised because doing it the way that they are used to doing multiplication, seems like it would be so much easier, an extension of something that they already know, but it didn't work that way! |
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Counts on fingers & toes
Posts: 12
| I show both methods and allow the students to use what works best for them. |
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Vertical method of multiplying polynominals
