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.