Teaching Factoring – Should we?

2007 August 19
by jd2718

There is a point of view that says that factoring is over-emphasized in algebra. I disagree strongly. Proponents of marginalizing or eliminating factoring make two major arguments.

1. Students don’t need factoring in order to do anything else. You know? Real-world wise, I buy it. But real-world wise, I can’t make a good argument for studying past per cents or making change. And I can’t make much of a real-world argument for most of what we teach, in most subject areas. But we expect knowledgeable adults, we expect young adults who can pursue studies in multiple areas, including those that are math-dependent, and we expect young adults who are conversant with a body of knowledge most of us share.

By deemphasizing and marginalizing factoring, we cheat our students.

2. The other argument is slick. Factoring, they put forward, is not necessary. The people who use this line agree that math is necessary, but usually focus on problems requiring numerical solutions: Set up the quadratic, use the formula or read approximate values from a graph. Let’s agree with them, but then ask, is factoring a useless skill? Of course not. Can it be avoided? Up to a point, perhaps, but you need to make a conscious effort to avoid it. Why not teach the skill?

(text continues below the fold —>)

Here’s what’s happening. 1. Factoring is hard. 2. We have a societal attitude that says innumeracy is okay. 3. We have an undercurrent that says cut out as much math as possible. 4. We have another trend that says challenge everyone (a reaction to racist tracking) and so 5. instead of saying, forget about math, we have anti-math people saying: forget about hard math. And 6. We have teachers who either find some topics difficult themselves, or who have limited flexibility in relation to teaching or reteaching more difficult topics. And the result: factoring and geometry proof are marginalized.

It ends up looking like this: more students do more math at the level of algebra and up than ever before, but watered down. The critics of difficult, procedure-heavy math have given us easier, procedure-heavy math. But more of the procedures are calculator keystrokes. And they are winning. Factoring in particular has been reduced to a secondary place in the curriculum. Most text books are written with factoring coming after parabolas and the quadratic formula, ie, intentionally shunting factoring aside. And the problems are too few and too basic.

This is, of course, the wrong answer. We should be teaching real factoring. Our curricula should develop the mathematics in a natural way, (the ordering in most books supports, instead, early introduction of topics without appropriate background, in order to do graphing earlier. Bravo TI! See what money buys?) with factoring preceding quadratics, and with both of them preceding parabolas. We should do our best to teach real math to all of our students, and we should recognize that some of our students will not have great success with some of the more difficult topics.

We should approach each student as if s/he has potential to study much more mathematics, and offer that student appropriately challenging work. When a student stumbles, we should provide support. And if a student eventually reaches harder math than they can handle, well, we have brought them as far as they will go (at that time). Far better to push a student to their limit, then to assume lack of ability in advance.

So I do teach factoring, fairly substantial factoring. In subsequent posts I will describe how I organize the topic (for bright high school students who don’t necessarily like math, and for weaker college students who are looking for the minimum amount of mathematics to graduate).

30 Responses leave one →
  1. 2007 August 19

    Excellent points! I agree with everything you wrote and could not say it better if I tried.

  2. 2007 August 20

    this looks like a pretty good summary
    of the situation to me; of course if
    i’d have said it it would have come out
    a great deal rantier.

    i’d like to see more “factoring” at the level
    of the natural numbers — i.e., number theory.
    i mean, not only the “tricks” (digit sums
    for multiples of three, e.g.), but the reasons
    they work (proofs! — some informality
    might be called for here, but proofs just the same).

    LCM and GCD could stand to be a lot better understood
    *before* one goes about extending ‘em to polynomials …

    oops. time for class. i’ll check in again later.

  3. 2007 August 21

    Vlorbik, I’ve learned to rant calmly. It’s really a skill that I had to practice at. I also found it necessary to read very carefully things I fully disagreed with so that I could poke at them without caricaturing them.

    Btw, if you haven’t looked before, peek at my pedagogy philosophy thing. I don’t have much time for the back to basics crowd, either.

    And thanks for the kind words, p.o. I can think of no higher praise than that of successful veteran math teachers.

  4. 2007 August 21

    And I love factoring numbers, and playing with the topic with kids. I squeeze bits into my algebra course: 3599 is a classic, but we also figure out which unit fractions terminate, and why, bits of LCM and GCM ab = LCM(a,b)*GCM(a,b) – they don’t know this but can well understand it, and other stuff, where I can squeeze it in. Little bits of modular arithmetic are nice, and while not directly factoring, learning to represent multiples and more than mulitples (ex 3n or 5n + 1) helps develop those lines of thinking.

    This year when I challenged kids to figure out this number trick we picked up on that same line of reasoning.

  5. 2007 August 23

    I absolutely agree that learning factoring is important. It provides a fundamental underlying many other processes in math, and even the process of learning it is beneficial, in my opinion.

  6. 2007 August 23

    3599 is a classic?
    news to me.
    you mean because it’s 60^2 – 1^2?
    (in case for some reason some
    *non* math-head is reading,
    i’ll point out that this fact “easily”
    implies that 3599 = (60-1)(60+1),
    i.e. 3599 = 59*61 [and that this is the
    *prime* factorization ...].)

    i seem to remember having to work out
    (a,b)*[a,b] = ab for an abstract algebra class.
    how it waited that long, i’ll never know.
    maybe somebody had shown me and
    i’d simply failed to pick up on it.
    anyhow, the proof of this fact
    (exponent juggling, of course)
    was very satisfying. still is, actually.
    it’s just a very cool fact.

  7. 2007 August 24

    LCD*GCD I learned somewhere in a math ed course. Of course it made all the sense in the world, I’d just not actually seen it before.

  8. 2007 September 1

    > “But real-world wise, I can’t make a good argument for studying past per cents or making change. And I can’t make much of a real-world argument for most of what we teach, in most subject areas.”

    The problem with this line of thought is that it leads to a ‘math for math’s sake’ mentality – the very mentality imposed on long-suffering students world-wide in a (dare I say it) clever attempt to retain math courses in schools where there may be no need. In Australia, for example, most students study calculus in senior high school (17 & 18 yrs old). But most won’t ever use this calculus.

    I used to teach math in the belief it was “good for them” until I started to concentrate on its utility. This was motivated by years and years of student retorts: “Why do we gotta do this?”. And I never really had a good answer.

    I started to examine the difference between “understanding” and “meaning” in math education. Most math classes concentrate on the “understanding” part, but very few bring any “meaning” to its study.

    I’m all for teaching factoring – but not just because…

    > “Can it be avoided? Up to a point, perhaps, but you need to make a conscious effort to avoid it. Why not teach the skill?”

  9. 2007 September 1

    Math is abstract. That’s what it is. Numbers are not physical objects. The moment you substitute physical objects for numbers, it’s not really math, and to teach whatever you wanted to teach, you need to abstract the quality “number” from the physical objects, eg pull the concept “four” out of the collection “paperclip, paperclip, paperclip, paperclip” It only gets worse from there. Objects can illustrate math, can help teach, but the moment they stand in the stead of the abstraction, the abstraction is lost.

    Math is for math’s sake if you want to be able to reapply it. Otherwise we get “how many lemons in seven groups of three?” “Sorry, we only learned pears.”

  10. 2008 February 15
    Lisa N permalink

    I came to the sight looking for a good reason for so much factor but still haven’t found one.

    As an engineer with a degree in math I find that I never factor anything. In the real world it is highly unlikely that I will ever run into such nicely contrived values that I would attempt to factor. I would do it numerically (or for a quadratic use the quadratic formula). There are so many other interesting approaches to take and mathematical ideas to explore, ones that could really help kids learn more general problem solving techniques. I have to disagree.

    I think too much factoring, turns people off from math. It really is a waste of time.

    P.S. in the “real world” we do a lot more that percents! but we don’t factor!

  11. 2008 February 15

    No one factors, except mathematicians. But we use factoring as we learn more advanced mathematics.

    You do everything numerically? And are convinced factoring is useless? Good for you. But don’t pretend you don’t have an opinion.

    And at least pretend to read the post and the comments next time.

  12. 2008 March 15
    D.Becker permalink

    Hi jd2718 I enjoyed reading this but have a question:
    I am curious why you favor factoring before graphing? My sequencing is as follows: real life parabolic behavior 2)basic Quadratics graphed, variations on quadratic eqns and their effects on parabolas 3) visually finding roots 4) factoring 5) quadratic formula 6) completing the square. The appreciation of factoring to find the root is a bit abstract without the visual of the x-intercept on the graph. At the freshman level where algebra 1 is generally taught I still find it important to begin with the visual side. Otherwise why factor? Introducing it as that which give the funciton no value I feel would be difficult in the beginning.

  13. 2008 March 16

    For algebra I we manipulate polynomials early (after learning to handle exponents). It takes time to get good at this.

    We graph lines later (parabolas, too). Mid-year.

    Late in the year, after learning to handle radicals, we tie all the strands up with solving quadratics by graphing, by factoring, by taking square roots, by formula.

    I note that you have work with two variables early. I also note that you have the quadratic formula before completing the square. You may have chosen (or your book may choose) to introduce topics that are easier and easier to motivate earlier.

    My focus, otoh, is on 1) justifying each topic mathematically and 2) introducing topics after students have had time to master requisite skills. The sequence you propose, imo, would not allow for either of these.

  14. 2008 July 23
    Mrs. F permalink

    Am I missing something? How do you simplify rational expressions without being able to factor? And this leads to finding holes in graphs of rational functions. Factoring is not just about solving quadratic equations.
    I’m in my 5th year of teaching and I’m beginning to struggle more and more with the usefulness of what I’m teaching, but I am determined that it has value.
    I don’t see many people who lie down and lift something heavy above their heads for a living, but I know millions of people who do bench presses religiously to build all sorts of muscles. Maybe math is this kind of exercise for the brain. An exercise in methodical, logical, sequential, rational thinking which we definitely could use more of (especially in politics). So a kid doesn’t ever factor again in his life. So what? She’ll use that logical, trial and error, scientific method a lot….I hope.

  15. 2009 August 30
    Math Teacher permalink

    I taught Algebra last year, and factoring has been cut from our Algebra 1 curriculum. And Proofs are not taught at our school at all. It’s in the curriculum, but since it’s not on the tests, the teacher doesn’t teach them.

    This year, I am now teaching Algebra 2 and Advanced Math and my students can’t factor at all.

    I think it’s terrrible! For me, factoring is a way of understanding number relations and understanding the basic concepts of math.

    I am definitely teaching factoring until my students get it! And am looking forward to starting it soon.

  16. 2009 November 11
    Debbie permalink

    Have you seen CME? It’s a new series of text books. Get at lots of real math. Doesn’t have enough practice problems, and at times can be a bit obtuse. But overall amazing. I just taught their Quadratics unit (from Algebra I) to an Algebra II class. Started with a numberic look at difference of perfect squares, moved on to factoring quadratics, then completing the square in a method that used difference of perfect squares along the way. Finally, they move on to graphing, and build on all the groundwork, making the vertex form seem obvious, since the kids are so used to it. And if you push it, you can even get them to see how the constants in the factors relate to the x-coordinate of the vertex. Check it out.

    -Debbie, math teacher, Waltham, MA

  17. 2009 November 29
    alex7 permalink

    We make comments on here as if all Algebra math courses are the same. We all serve different populations. For my group of kids, spending a month explaining, understanding, and working on factoring would be a waste of a month that could be better spent on other aspects of the math curriculum. Why? Because I have far too many algebra students who still are confused by negative numbers, dividing fractions, and exponents.

    Who’s fault? Many factors, but I’m not going to lose 80% of the class’ attention by forcing the guess-and-check factoring simply because it’s the month of the year where we normally work on that.

    Part of teaching to depth, to mastery, may include shortening or running out of time to teach certain math aspects. It’s just life in some school’s situations.

    If I had a bunch of self-motivated students with computer access at home and a solid history in their previous math courses, then yes, factoring – if nothing else- would be a great brain exercise (reasoning, organizing, etc) that could later be applied in other realms of life.

    • 2009 November 29

      What population do you serve?

      There are real issues with forcing students who are not algebra-ready into algebra. Part of the reaction in California, if I understand correctly, did exactly that.

      • 2009 December 10
        alex7 permalink

        I work at a school where we help students that for whatever reason weren’t able to stay at the traditional high schools. Some have kids, others are homeless, some were in trouble with the law.

        However, it seems that even in “normal” algebra courses, too many kids were of the “skimmed by and got a C” pre-algebra kids.

        It does seem help is on the way with the upcoming streamlined teaching standards.

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