Wednesday, February 17, 2016

Domain and Range

In previous years I've always taught Domain and Range when I taught Graphing Functions/Equations (see my previous post) and it was enough for my students to grasp the concept.  However my Algebra 1 group last year, and again this year, needed so much more than what I've previously done.  Some years they are able to catch on quickly while other years need more explanation and practice.  So prior to my Graphing Functions/Equations page I designed one that just focused on Domain and Range to help these groups out.

We started with how to identify Domain and Range, what's the proper way and what happens if a number repeats.

I had the students pick two colored highlighters (one for domain and one for range).  I use a lot of color on my pages but it's always for a good reason.  We don't ever just use color to use it.

As a whole class we went through the different situations they would be presented with: XY Table, Set of Ordered Pairs, Maps, or a Graph.

For the XY Table they had to highlight the Domain and Range then write them in proper order.

For the Ordered Pairs they had to highlight each number that represented the Domain and which ones represented the Range. Then write them in proper order.

For the Map they had to again highlight the Domain and Range then put them in order.

The Graph took a bit more effort on our part.  I gave my students the option to either write out each point as an ordered pair or we could make it into an XY Table.  They prefered the table and found it easier to use so we went with it.  They again had to highlight and write the Domain and Range in proper order.

On the right side of the notebook we defined Domain and Range and then they were given the 5 different examples.  For each they were asked to find the Domain and Range.  Some understood it and no longer needed to use the highlighters while others relied on them for quite awhile. I always allow my students to use materials like highlighters and such on their progress checks, so some of them were still using it even on progress check day while most had stopped using them long before.

This is how the pages look side by side.  How do you teach Domain and Range?  What tricks do you use to help them remember the difference?  I'm always up for some new, fun ideas :)


  1. This looks like a great lesson! I particularly like the intentional color-coding and multiple representations to solidify their understanding of concept. I find that students are often introduced to domain and range briefly and generally, so they don't have the time to make those connections. As I support students with math, I find they often forget which one relates to the x-values and which relates to the y-values. I know this is a small "trick," but I remind them to think of the alphabet to remember that domain comes before range as x comes before y. I don't like resorting to these types of tricks, but it's a small trigger to connect the vocabulary to the symbols. I look forward to trying your approach next time around!

  2. Thank you for sharing. I like the use of color to help identify the domain and range.


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