Algebra 1: Representations of Linear Equations

Increasing my students' representational fluency has been something I've been working on for a while.  Our second semester started last Monday, and to start my Algebra 1 students off easy, I had them do a four-fold poster of a linear relationship to review what we did last semester: situation, equation, table, and graph.  They did the work fine overall, but quite a few students had more troubling questions than I had expected (i.e. "how do you make a table?").   I guess it just shows that we have to keep going through these different representations and their connections again and again.

We have started the new unit - working with linear equations - in which students have to write the equation of a line given its slope and a point, or two points, or a point and a parallel line.  In the past, I have done this only algebraically (except for the initial explanation of concepts); this time around, the students will have to practice the problems both algebraically and graphically.  And, more importantly, the skills tests will require them to show mastery with both methods.  Let's build those connections!

Here are the first few lessons in the unit.

Lesson 1 (Representations of Linear Functions)
Lesson 2 (Graphing Practice)
Lesson 3 (Write the Equation of a Line)
Lesson 3: Keynote / Powerpoint

And some snippets from the worksheets to illustrate what I am talking about:

 

Introducing Linear Inequalities

To show that a line is a representation of an infinite number of points, I like to give my algebra 1 classes an equation, like y = 2x + 3, and then give each student a couple of different ordered pairs - some that are solutions and some that aren't.  I have them each work out their points, and then go to the board to plot an open or closed circle, depending.  Once all the students sit back down, we look for patterns and see that all the closed circles fell on a straight line.  Discuss, and voila.

This extends nicely to linear inequalities (and systems of equations and inequalities).  On Tuesday, my algebra 2 students were reviewing linear inequalities so I did this activity with them.  I really like it, because it is engaging, and it helps build a mental picture that they can rely on later on when they are struggling through graphing problems on their own.  My students often get stuck on the "pick a test point" part of the process; but now, I ask them if they would have plotted a closed or open circle based on their result, and to think about what the picture on the board looked like.  This usually helps them see which side of the boundary line to shade, and to be able to explain why.

Here is what the board looks like after students plotted their points:

Then, we looked for patterns.  Usually, a student will come to the board and draw some sort of line after getting frustrated with trying to explain it in words.  Then I reveal the shading:

And there are usually some audible "ahhs" and such.  Another great benefit of this is that the string of open circles on the boundary helps students see what the dotted line is all about, and why changing the inequality to include an equals sign would create a solid line - a string of closed circles.

Here is my lesson that goes with this.  And the keynote.

Algebra 1: Graphing Lines Practice

I just used this worksheet from Mr. K for the first time the other day.  I thought it had a pretty cool setup, but I didn't realize just how effective it would be until I used it in my first class.  The "solve the joke" aspect of it helps draw them in, but the hidden beauty is in its self-checking properties.  Since each line must pass through exactly one number and one letter, a line that doesn't do this must be graphed incorrectly.  Students started realizing this and would go back and find mistakes without having to check with an answer key.  The only bad part (sorry to say) is that they had absolutely no idea what the answer was supposed to mean (see earlier post).

I made up a "balloon pop" homework to go with this that was inspired by Green Globs.  I wish I had the tech access for my students play that game.

Algebra 1: Skills List - Spring Semester

I spent a good deal of time right before break trying to figure out exactly how far I can push my students for the second semester of Algebra 1.   These skill items will be broken down into chunks for the skills tests, and MC-ized for the benchmarks and final exam.  I regret how many concepts I had to leave out due to time pressures; and still, the list seems daunting and endless.

If you're interested, this is what my students will be doing over the coming months.

doc / pdf

ELL Joke Worksheets?

Kate wrote a great post about the value of a well-structured worksheet last month.

I agree that there are huge benefits of having a unified task, with some type of self-checking or affirmation. And a little fun and/or creativity doesn't hurt. Joke worksheets do that pretty well. However, my students (who are generally not native English speakers) hardly ever get the joke. They tackle the sheet with excitement, but there is usually that little moment of disappointment at the end when they don't get the punchline. Instead, of course, of the expected groan and eye-roll that accompanies a quality pun.

"What do you get when you mix prune juice with holy water?"
"A religious movement"

After two minutes of explanation, that loses some of its original zing.

So my question is if anyone has or knows about these kinds of worksheets developed for ELL students? I'm kind of doubting that there are any, but it never hurts to ask. I think I will probably end up creating some next semester, with jokes solicited from my students. Then I can publish the DCP Spanglish Algebra Joke Book.

Algebra 1: Situation Graphing

I learned a few years back that jumping right into graphing slope-intercept equations never worked. This is one of those concepts that, before I became a math teacher, I never would have guessed would be so hard for students to master. Start at the y-intercept, use the rate of change to plot the next point, and you're done - right? Yeah, not really. So after a couple of years of teaching, reteaching, re-reteaching, and tearing my hair out, I decided to try some other things. Eventually, I realized that a ton of scaffolding of the concept of slope was needed, along with firmly rooting linear functions in situated contexts.

One of the constant problem areas is deciding which way to draw the line for a negative slope. To graph something like y = -(2/3)x + 5, students would often move down 2 and left 3. My old attempts at correcting this focused only on the mathematical explanation: -(2/3) = -2/3 = 2/-3. So, you either go down 2 and right 3, or up 2 and left 3. If you go down 2 and left 3, that means -2/-3, which is 2/3. This is a perfectly reasonable way to explain it, but it didn't really provide much of a lifeline to my lower-skilled students, as it hinges on mastery of the division rules of signs, as well as remembering that a fraction also represents a division problem.

The other common problem was for students to correctly identify the starting point number, but to plot it on the x-axis instead of the y-axis.

The way I run the unit now is to provide numerous opportunities to graph and describe situations, both with and without numbers, in just the first quadrant of the coordinate plane. Distance, income, height, and so on. The quantity being measured is always on the vertical axis, and the horizontal axis always represents time. When we eventually generalize to y = mx + b equations on the full coordinate plane, I use the situated contexts as memory anchors. If a student doesn't remember where to start, I say something like, "Where do we show that the Hare got a two foot head start? On the feet axis or on the seconds axis?" In these situations, a positive rate of change always means "moving up" and a negative rate of change always means "moving down", while time is always passing to the right. This is a much more helpful way for my students to think about how to graph their decontextualized lines. Suddenly, there is a reason for the direction the line is moving in, instead of just a sign rule.

Another benefit to this approach is that my students are now a lot more flexible with the form of the equations. My situated equations typically are in the form y = b + mx, which seems like a more natural connection to the preferred method for graphing. Once they grasp that the number without the variable is always the starting point, then they can handle both y = b + mx and y = mx + b relatively interchangeably. Also, it really helps them to understand the difference between equations like y = 2 and y = 2x. The first shows a starting point of 2, with zero rate of change. What does it look like on a graph if someone is not moving, but time is still passing? Exactly - a straight line! (I'm still working on that one - even my highest skilled students still say straight when they mean horizontal. My "all lines are straight" response doesn't usually clarify the way I'd like it to.) And in the second, the rate of change is 2. Ahh, it's like a graph of someone running 2 feet per second... but where did he start from? Zero? Where is that?

This approach takes a ton more time, of course, but I can't see any way around it for my students. I hope that I am providing them with a long-lasting ability to understand and graph linear functions. The semester is ending this week (final exams start tomorrow!), so the test will be to see how much they recall in January, when we move into the next unit. We'll be doing those oh-so-fun problems where you give them a point and a slope (or a parallel line and a point, or two points) and they have to give you the equation of the line. I'm going to experiment with doing every problem both graphically and algebraically (both in instruction and on assessments) to see if the focus on multiple representations helps them master these problems. I'll post more about that in late January (after I develop and teach it!).

My Slope and Graphing Linear Functions unit (Unit 4) is pretty much up-to-date in my box.com widget in the side bar. Here are a couple of examples (in pdf format) of the kinds of activities that they were doing. The Word and Keynote files are all in my box. I'd love to get feedback on any of this.

Lesson 10: Practice graphing with tables
Lesson 11: Learning to graph without tables

Review game: Trashketball

I know that many teachers out there play some form of Trashketball, so this isn't really groundbreaking. However, I always have problems with these kinds of review games. Structuring them so that the higher-skilled students don't dominate or pressure the other students can be quite difficult. Or, looking at it the other way, there are plenty of lower-skilled students who are happy to sit back and let others on their team get the work done for them.

I developed Tic Tac Toe Battle Royale a couple years ago which addresses some of these concerns pretty well. But you can only do the same game so many times. My experiments with Trashketball in the past haven't been that successful, and so I thought about how I could improve it to work more effectively in my class. This is what I came up with:

1. Break students into groups of 3 or 4 - for me, this yields no more than 6 groups in my Algebra 1 classes. Give each group a letter, and each person in the group a number. Write these in a grid on the board. (If there is an unfilled spot in a group, that spot becomes a wild card - any person can take that number.)
   
2. For each round, create 6 separate problems that all target the same concept, but that are slightly different. This prevents the copying problem found in board races.
3. Hand out a template for doing the work on. My freshmen need an organizer for everything. "Get out a sheet of paper" just doesn't fly.
4. Show the 6 versions of the problem, giving the class enough time to get it done.
5. Call for silence. Block the projector. Randomly (or not) call a number between 1 and 4. The student in each group with that number comes to the board - all 6 at once. Have the board sectioned off so they know where to write. They are allowed to bring their own graphic organizer up with them, but no one on the team may offer help at this point. The idea here, of course, is that students must make sure that all group members have done the work. Students who tend to slack off have to at least write down the work that others in their group are doing. Not ideal, but it's better than spacing out.
6. Have the trashketball basket set up. As students complete their work on the board, tell them if they are right or not (make sure to have answer keys ready!). Right answers get a point, and they get to take a shot for a bonus point. There is less waiting around time this way - some students will still be writing their problems as others are already lining up to shoot.
7. Record the scores and move on. Winning team gets a whatever.

How it looks:


I did this for the first time today, and was amazed by how well they did. There were only 2 students in the class that I couldn't get totally engaged. The rest did all their work, were excited to take their shots, and so on. It takes longer to make this activity due to the multiple problems, but it was really worth it. Man, do they love tossing paper balls into the recycle bin.

I know it kind of breaks my respect class norm, but it really warms my heart to hear a kid (who I can usually barely get to sit down, and who really wanted to win) say to his teammate who hadn't done his work on the board carefully: "Fool! I told you it was negative eleven!"

Trashketball Problems (Keynote) (Powerpoint)
Answer Template (Word)

Math Department Photo: 2009-2010

Michelle Longosz, our former photo teacher, always takes amazing department photos for us each year. Here is the radical math department.

XKCD based lesson: The Coordinate Plane

Ever since I first saw this xkcd cartoon, I wanted to use it in a lesson. I finally put that together this year. I used the cartoon as a way to help convey the idea that points on a coordinate plane are a way to easily visualize the relationship between two different variables. The purpose of the numbers is simply to quantify those relationships, if such a quantification is necessary. I then had students make their own graphs for homework, with variables of their choice. If I had more time to spare, it would have been nice to do this in class (and the outcome would have been better, I think).

This lesson (Unit 4, Lesson 5) and others can be found in my box.com widget to the left. I recently updated Algebra 1, Units 3 and 4.

Here are some examples of the students' work.

Story of 1

I was clued in to the existence of The Story of 1 a couple of weeks ago from my twitter PLN. I had my sub show it to my algebra 1 classes when I was out of town, and it seemed to go well. Then, one of my colleagues was sick this week and did the same lesson. Her sub said that the students were really engaged with the movie. I couldn't find a question guide on-line for it (though I didn't search all that long), so I made one up.