Recent Quadratics Stuffs from Algebra II

I am just finishing up my quadratics unit in Algebra II. We spend a lot of time on quadratics, doing everything from factoring, to completing the square, to the quadratic formula, to all sorts of graphing, the discriminant, 1D and 2D quadratic inequalities, quadratic linear systems, systems of inequalities, etc. Tons. And we didn’t even get to do the project I enjoy involving pendulums and quadratic regressions. Le sigh.

I’ve posted much of my quadratics materials before, but I thought I’d share some new/updated ones. I’m a bit exhausted, so forgive the shortness of my descriptions.

1. My Vertex Form worksheet was motivated by my frustration with students just memorizing that y=(x-2)^2+3 has a vertex of (2,3) because you “switch the sign of the -2 and keep the 3.” Barf. (FYI: we haven’t done function transformations yet.) So I created this sheet to “guide” students to a deeper understanding of vertex form.

[.doc]

2. My Angry Birds activity was inspired by Sean Sweeney, but modified. I had taught students how to graph (by hand) quadratics of the form y=x^2+bx+c and y=-x^2+bx+c. Students also had been exposed to the vertex form of these basic quadratics. But they hadn’t been exposed to quadratics where the coefficient in front of the x^2 term wasn’t “nice.” So all I did was give them four geogebra files, and had them play around. By the end of the activity, students recognized how critical the “a” coefficient was to the shape of the parabola, they started conjecturing that if you had the “a” value and the vertex and whether the parabola opens up/down that you could graph any parabola, and one pair of kids were able to convert a crazy angrybirds quadratic (with a really nasty “a”‘ value) to vertex form.

[.doc] [files]

If I’m teaching Algebra II next year, I want to ask if I can get rid of quadratic inequalities or some of the other more technical things we do, and make an entire unit/investigation on using geogebra and algebra and angrybirds to investigate quadratics.

3. My discriminant worksheet is below. It worked okay, but students still didn’t quite understand the difference between y=ax^2+bx+c and 0=ax^2+bx+c, which was the goal of the sheet. So it needs some refinement.

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[doc]

4. Finally, below are my attempts to get students to better understand quadratic inequalities. I started with a general sheet on “visualizing function inequalities,” and then I made a guided sheet to bring more detail to things. I found out that students didn’t quite understand the meaning of the schematic diagram we drew, nor did they understand why to solve 0<x^2-4x+3 we have to draw a 2D graph. Well, to be more specific, students could do the process but didn’t fully grasp why we graph y=x^2-4x+3. I changed up this worksheet this year, but maybe I should go back to last year’s worksheet.

[doc]

[doc]

C’est tout. With that, I’m exhausted and going to bed.

A Time Capsule

I had this idea, and I wanted to throw it down before I lost it. It may be nothing, or it may be something awesome.

I have been mulling over if I should do a project in calculus in the fourth quarter. And I had a thought. I have been really trying to focus on the fundamental underlying ideas in calculus, and shooing away the algebraic gobblygunk. Why? Because my kids aren’t taking AP Calculus. Most won’t be taking math in college. So I want my kids to leave calculus saying: “Yes, I understood the ideas. Calculus is about ideas.”

I wonder if a good final project, which would force them to grapple with the Big Ideas, might be having students create a collective time capsule, which will be stored in some deep underground facility, and will be the only remnants of “Calculus” that may exist after some horribly apocalyptic disaster.

I’m not sure what would go in the capsule, but I like the idea that all students would be asked to contribute a few items. Maybe we’d break the course into chunks, and each student would be responsible for writing an accessible explanation of each chunk — and we bind these together into a book? And each student would create set of drawings/graphs/photograph/images that (for them) represent the Big Ideas of Calculus, and they have to explain each one of them… What’s the idea, and why is it so important?

In addition to these required items, students could have their choice of what else to contribute… Things like:

1) A video of the student explaining the weirdnesses/paradoxes/strange ideas of (or relating to) calculus
2) A short research paper on the history of calculus
3) A letter to the future explaining why calculus is an important swath of knowledge that shouldn’t be forgotten (including uses / applications of calculus)
4) A challenging calculus problem, and it’s solution
5) A “concept map” for calculus
6) Audio recordings of students reading quotations about calculus that resonated with them, and then students explaining why it resonted with them.
7) Designing a cover to the collective calculus book we bound together, and on the back cover, an explanation of how the cover exemplifies the course

Or other things?

I don’t know. It felt like a cool idea when it jumped in my head a few minutes ago, but now that I’m writing it, I can’t quite picture it … yet. Any ideas of how to take this idea and turn it into something good? Throw it in the comments!

Two crazy good Do Nows

Recently, I’ve been trying to be super duper conscientious of every part of my lesson. For example, I wrote out comprehensive solutions to some calculus homework, paired my kids up, handed each pair a single solution set, and had them discuss their own work/the places they got stuck/the solutions. I actually had made enough copies for each person, but I very intentionally gave each pair a single solution set. It got kids talking. (Afterwards, I told them I actually had copies for each of them.) That’s what I’m talking about — the craft of teaching. I don’t always think this deeply about my actions, but when I do, the classes always go so much better.

In that vein, of super thoughtful intentional stuffs, I wanted to share two crazy good “do nows” from last week. Not because they’re deep, but because they were so thought-out.

For one calculus class, I needed my kids to remember how to solve 5\ln(x)+1=0 (that equation was going to pop up later in the lesson and they were going to have to know how to solve it). I also know my kids are terrified of logs, but they actually do know how to solve them.

I threw the slide below up, I gave them 2 minutes, and by the end, all my kids knew how to solve it. I didn’t say a word to them. Most didn’t say a word to anyone else.

How I got them to remember how to solve that in 120 seconds, without any talking, when they are terrified of logarithms and haven’t seen them in a looong while?

I can’t quite articulate it, but I’m more proud of this single slide than a lot of other things I’ve made as a teacher. (Which is pretty much everything.)  Not deep, I know. It’s not teaching logs or getting at the underlying concept, I know. But for what I intended to do, recall prior knowledge, this was utter perfection. The flow from each problem to the next… it’s subtle. To me, anyway, it was a thing of perfection and beauty.

The second slide is below, and I threw it up before we started talking about absolute maximums/minimum in calculus.

As you can imagine, we had some good conversations. We talked about (again) whether 0.9999999… is equal to 1 or not (it is). We talked about a property of the real numbers that between any two numbers you can always find another number (dense!). I even mentioned the idea of nonstandard analysis and hyperreal numbers.

So I know it isn’t anything “special” but I was proud of these and wanted to share.

Infection Points: The Shape of a Graph

Everyone here knows that I think Bowman Dickson is the bee’s knees, the cat’s pajamas, ovaltine! Recently he posted about how he introduces inflections points in his calculus class… and just a couple days later, I was about to introduce how we use calculus to find out what a function looks like.

Usually, I introduce this in a really unengaging lecture-format. But he inspired me to … copy him. And so I did, extending some of his work, and I have had an amazing few days in calculus. So I thought I’d share it with you.

The Main Point of this Post: By creating the need for a word to talk about inflection points on graphs, we actually saw the math arise naturally. And through interrogating inflection points, we were able to articulate a general understanding of concavity. In other words… the activity we did motivated the need for more general mathematical concepts.

First, definitely read Bowman’s post. All I did was formalize it, and extend it in a few ways, by making a worksheet. I put my kids in pairs and I had them work on it (.docx):

What naturally will happen when students generate their graphs is they will get a logistic function. (Which has a beautiful inflection point! But they don’t know the word… they just see the graph.)

So here we are. The students have a graph, and they’ve been asked to explain their graph for (a) the layperson and (b) the mathematician. Most get some of it done with their partners, and then they take it home to finish individually.

The next day, at the start of class, I assign students to work in groups of 3 (with different people than their partners the previous day). They are asked to take a giant whiteboard and:

(Now I want to give credit where credit is due. I have really been struggling with using the giant whiteboards well, and having students present their work effectively and efficiently. My dear friend Susanna, when I told her about this activity, suggested the groups, the underlining of the mathy words, etc.)

This worked splendedly.

(click to enlarge)

And they had such great observations. Some groups picked up on that change where the function was increasing in one way to increasing a different way. Others talked about how the rate of change (of infected over time) was greatest. Others talked about how the function was “exponential” for the first thing, seemingly linear for the middle third, and “something else” for the last third.

Those gave rise to good short discussions, and we came up with the language for inflection points (which I call INFECTION POINTS!!! GET IT!?!) and concave up/down.

After they had a sense what those words meant, I had students work in partners on the following (.docx):

The point was to get students comfortable with the ideas before we delve into the heavy mathematical lifting. It was powerful. Especially the last page, which got students thinking about patterns, exceptions, and ways to generalize. Our big conclusions:

And with that, I’m too exhausted to type more. But that’s the general sense of what went on in an attempt to teach how to use calculus to analyze the shape of a function.

An important question: how do you plan?

I don’t think I’ve seen this asked before, and … well, I need to crowdsource something.

Tonight, on twitter, I asked:

For the past few weeks, I feel like my teaching hasn’t been that good. It’s okay, but not near the level of goodness I know I could achieve. My big limiting factor is time and energy — I’m overextended with commitments. But I also think I could be doing better if my planning process were better. If it were more efficient, and I reoriented the way I thought of how I plan…

So I’m wondering from y’all, on a regular basis for a normal class…

… and before you answer, this is a judgment free zone! If you wing it and don’t plan most days, just say that! I just want to get a sense of what people do to see if I can’t steal some great ideas and be a more effective planner … and I guess I’m also just plain plum curious!

(1) How do you plan? Like… um… what’s your process (if you have a formal one), or what do you do (if you just sort of do something)?

(Things like: what sort of things do you think about when you’re planning? Do you pre-script questions? Do you pick specific problems? Do you design some conceptual walk-through for the kids? Do you always build in formative feedback? Do you always try to switch what kids do 2 or 3 times a class? Do you start with a unit or week-long plan and then go down to the individual class level, or vice versa?, etc.)

(2) What does your completed plan look like? Is it written on paper, or a SmartBoard file, or a computer file, or in your head, or something else — and what sorts of things are on it? Questions? Objectives? Problems?

(3) How much time does it take you (again, for a normal class, on a normal day) to make a plan for a single day’s class?

(4) Other stuff that didn’t get caught in the net of the first three questions, but you wanted to say?

Throw your answers in the comments! Help me out!

 

A guest lecturer…

Last year I had this student who struggled in Algebra II. And then, one day, he decided he hated struggling. He was frustrated and didn’t want to be frustrated anymore. He wanted to get math. And so… he did. To the point where he was getting almost perfects on assessments.

This was a student who I always thought highly of (I knew him both inside and outside of the classroom), and when he was frustrated, I felt for him. And when he made a dramatic turnaround, I couldn’t have been more elated. I have to say, there are some students who you just want to ask you to write college recommendations for. And these college recommendations just roll off the keyboard. He asked me, and I remember sitting down, and going at it. I think it ended up being two and a half pages, and I had to edit it down to be that. He exemplified the transformation that I hope all my struggling kids go through, but his transformation was the most dramatic of all my students last year.

Because I wanted my kids this year to know that they can struggle, and come through the other side, I invited this student to come talk to my class for a few minutes and talk about his frustrations. And how he made his transformation. I want to show my kids that they can be more successful, but there is no royal road to mathematics. The way to be successful is to work hard.

The key points that my former student made when talking to my kids:

  • One day, one moment, he said “enough’s enough.” And he made a decision to do well in math. He was sick of that low grade on his report card, year after year. It was this moment that changed it all, because he changed his mindset to “I can’t do it” to “I will do it.”
  • He said that doing well in math has a lot to do with confidence. He didn’t have a lot of confidence, but slowly when things began to turn around, he became slightly more confident. And then more confident. And now, this year, he is overconfident in math.
  • He said that those annoying “explain this” questions that Mr. Shah asked were… annoying. But once he learned why I was asking them, that I was trying to get him to understand more than procedures, but to draw connections and see everything fit together, they made sense.
  • He stopped looking at each test as something that needed to be crammed for the night before. Instead, each night he would work on understanding the material. And when doing this, he saw connections.
  • He entreated my kids this year to try to draw connections between everything we’ve learned. Because that’s how it all hangs together. That’s what made everything click for him.
  • He also said that even though he failed the first five binder checks, he finally figured it out. And he could be organized.

I don’t know if his message got through to any of my kids, but I do know that me saying these things isn’t going to do as much as a kid who went through the trenches and came out a hero.

So if you want to honor a kid who was awesome, and maybe (possibly?) get through to your class, think about inviting a former student to give a short guest lecture!

PS. I have former calculus students stop by all the time, and I always make them come to class. Sometimes I’ll leave the room and have the student talk to the class alone, about what recommendations they might have for my current students, sometimes I’ll stay, and sometimes I’ll have ’em talk about college life, and how everyone gets through the college application process, and how truly there is light at the end of the tunnel (even when it may not feel that way).

Implicit Differentiation

Normally, I don’t have trouble teaching implicit differentiation. However, I’m never satisfied with what I do. I’m fairly certain that I have taught it four different ways in the past four years. But what’s common is that we do a lot of algebra. By the end, they can find \frac{dy}{dx} for a relation like \sin(xy)+y^3=2x+y. Or something like that. But we lose the meaning of what we’re doing.

I realized we can do all this algebra, but it’s all procedure. And so there’s no real depth.

So today, after introducing implicit differentiation (including some visual motivation), I assigned 5 basic problems from the textbook. Each of the problems has an equation like 3y^3+x^2=5 and students are asked to find \frac{dy}{dx}. My kids are going to go home today and struggle with it. We’ll spend about 20 or 25 minutes in our next class going over their solutions, talking about things, whatever.

And then… then… I’m going to hand out this sheet I wrote today.

[.doc, .pdf]
[if you’re wondering, the graphs were made by the fabulous winplot which I adore… it can do implicit plotting!]

My kids found \frac{dy}{dx} for homework. Now in class, my kids are going to interrogate what that means.

I am not sure yet how I’m going to structure the class. I think I might have us all work together on the first problem (#9), and then assign pairs to work on two of the remaining problems. And then I’ll pick one problem for each pair to present to the class. But what I’m truly happy about is that each problem gets kids to relate implicit differentiation to a graphical understanding of the derivative. It forces my kids to look at the derivative equation, and make connections to the original graph.

Although I’m proud of it, I’m honestly just not sure if this investigation is beyond the scope of my kids’s abilities. It pulls together a lot of concepts. I think it’ll work for them. This year I have a really really strong crew so I have faith. However, it’s an activity I’m going to have to give my kids time to do, and room to struggle. I know me, and I’m going to want to rush it, and I’m going to want to help them in ways that aren’t good for them. The struggle is where they’re going to learn in this, so I have to give it time and stay out.

I am in the middle of a hellish week, but if I have time, I’ll try to report back how it goes after we do it in class.