I learned a nifty domain and range trick from an online workshop about using stickie notes to help “frame” the graph of a function. The idea is to use 4 notes so that all you see is the graph, which can make identifying the domain and range a little easier.
Slide a stickie note from left to right until you “bump into” the function, and stick it on the paper. Likewise, slide a stickie from right to left, top to bottom, and bottom to top, until the graph is framed, like so:
Now, students can see that the domain can be expressed as -5 ≤ x < 5 and the range can be expressed as 0 ≤ y < 6 (It’s easier to see on a graph whose axes are numbered a little better, but you get the idea if you peek at the original graph above).
I like the strategy a lot – it’s tough for kids to visualize domain and range with the plethora of unusual and squiggly graphs out there. Since I’m guessing most of my students won’t walk into the EOC with Post-Its in their pockets, I like using highlighters to color-code things a bit. Here are several work samples from students today showing their different interpretations of the strategy. I like how they took the stickie strategy and made it more practical based on the writing tools they *will* have when taking the Algebra 1 EOC next week.
Check out this idea I found on Pinterest – another nifty way to help students visualize domain and range: