## Function, Expression, Equation Poster

The other day, Sarah showed me this tweet, and told me she wanted to make a poster based on it:

She wasn’t sure how she would do it. I tried suggesting an idea I had, but we decided it might be easier if I just made it and let Sarah see what she thought. Turns out that she loved it:

She did get it laminated today, and it looks like this:

What I love about this is the way it demonstrates the differences between functions, expressions and equations, but also shows how there’s a connection between them too. This poster goes well with the set Sarah created about solutions, roots, zeros and x-intercepts; that’s how she’s got them in her room, after all!

Now, the poster doesn’t capture all the particulars of these algebraic tools; it’s just a simple poster showing one example. There were some comments on twitter about the fact this poster doesn’t completely define what a function is, particularly absent a discussion of sets. Also, there was concern that the equation example implies all equations are homogeneous. Both criticisms have an element of truth, but also miss the point of a poster that, by its nature, only has one example. I think posters serve the best as either reminders of topics already discussed or starting points to launch a deeper discussion or investigation. Please, never put a poster on a wall and assume that means you’ve taught a topic. For an example of how I’ve discussed functions before, see these notes that I used in Algebra 2 last year.

This one may be a little tricky to put together, so if you want some guidance, keep reading:

1. Choose your three colors. The effect works best (and helps communicate the idea) if the middle color appears to be a blend of the other two. If you don’t want to think too hard, just use blue-green-yellow like me, but I’d love to see other color combinations too.
2. Print the first page (function) on the first color (blue, in my case), and the second page (equation) on the last color (yellow).
3. Print either page on the middle color (green). For this page, you only need the expression rectangle, which appears on both pages. Cut off the rest of the paper.
4. Stack your three pages with the expression rectangle of each page overlapping, with the middle color on top. Make sure you line up the rectangles as perfectly as you can.

These are the notes I wrote for adding and subtracting rational expressions last year in Algebra 2.

On the first page, I wanted to make the connection between rational expressions and fractions explicit, so I started with a reminder of how to add and subtract fractions. The two examples were chosen deliberately; the first only required changing the denominator on one fraction, while the other required changing both denominators. Students need to deal with both types of problems with rational expressions.

The next part introduced two simple problems, with only one denominator being changed between them. They are both problems that require simplifying, as I wanted to emphasize the need to do this from the start. (Students had already seen how to simplify rational expressions and stating excluded values.)

The next page was about finding the lowest common multiple. I had students use a strategy which emphasizes the definition of the LCM, having them multiply by factors so that the two expressions are the same.

And finally, a couple of examples putting all of this together.

## Algebra 2 Practice Book ver 0.2.0

Summer means I have lots of free time to work on my book! Well, sort of. We’re in the middle of getting ready to move, so that’s taking up most of our time. But, there is more free time than normal, so I have managed to make some progress.

The major change is the addition of chapter 1, which is about the fundamentals of functions, with a particular focus on transformations. The only standard parent functions dealt with here are linear and absolute value functions, as this is an introduction to the principles that will be used with other functions in the following chapters.

I’ve rearranged some of the chapters in this revision, so the numbering is a little different than version 0.1.1 (that’s why I bumped up the minor version number.)

I am hoping that I will have chapter 2 written in the next few weeks, which will introduce quadratic and cubic functions.

Mr. Carter’s Algebra 2 Practice Book
Version 0.2.0 (June 2, 2018)

Chapter 1: Functions

Chapter 3: Polynomials Part A (formerly Chapter 5)

Chapter 4: Polynomials Part B (formerly Chapter 4)

These are early drafts of what is very much a work in progress. All content is subject to change.

Copyright Shaun Carter © 2018. Teachers may reproduce these documents for use in their own classroom only.

## Analyzing Polynomial Graphs

Here’s an INB page I created to introduce students to analyzing graphs of polynomials.

Each graph is repeated three times, so we can (literally) highlight different aspects of it. Luckily for me, Sarah is amazing at acquiring classroom supplies, so I have a lot of highlighters for students to use.

The first part was identifying the x-intercepts and the nature of each of the intercepts. I had students highlight the curve around each intercept, to emphasize whether they are simple intercepts, vertices (local minima or maxima) or inflection points.

As students did this, I tried to direct the conversation to figuring out why particular polynomials led to particular types of intercepts. This was actually really easy, as the class were asking and answering these questions without much prompting from me at all.

Next, we found the intervals for which each polynomial is positive, and for which they are negative. Having students visually represent the sections which are positive and negative really helped them in identifying those intervals.

I just (as in, while I’m writing this post) had an additional  idea to help with this part. If I’d given each student a card, they could place the edge of it along the x-axis so that only the positive parts of the graph were showing. They’d highlight those parts of the curve, then flip it over so they could highlight the negative parts of the curve.

Finally, they highlighted the sections which were increasing, and the sections which were decreasing. To find each local maximum and minimum, I just had to quickly teach them some differential calculus…

… just kidding. We used Desmos.

Joking aside, I do like using topics like this to start hinting at the math that students may be seeing in the future. I was able to explain that a big part of calculus is looking at the rate and direction of functions, with a particular focus on where functions are neither increasing or decreasing.