Engaging students: Solving systems of linear inequalities

In my capstone class for future secondary math teachers, I ask my students to come up with ideas for engaging their students with different topics in the secondary mathematics curriculum. In other words, the point of the assignment was not to devise a full-blown lesson plan on this topic. Instead, I asked my students to think about three different ways of getting their students interested in the topic in the first place.

I plan to share some of the best of these ideas on this blog (after asking my students’ permission, of course).

This student submission again comes from my former student Heidee Nicoll. Her topic, from Algebra: solving linear systems of inequalities.

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How could you as a teacher create an activity or project that involves your topic?

I found a fun activity on a high school math teacher’s blog that makes solving systems of linear inequalities rather exciting.

Link: (https://livelovelaughteach.files.wordpress.com/2013/09/treasure-hunt1.pdf)

The students are given a map of the U.S. with a grid and axes over the top, and their goal is to find where the treasure is hidden.  At the bottom of the page there are six possible places the treasure has been buried, marked by points on the map.  The students identify the six coordinate points, and then use the given system of inequalities to find the buried treasure.  This teacher’s worksheet has six equations, and once the students have graphed all of them, the solution contains only one of the six possible burial points.  I think this activity would be very engaging and interesting for the students.  Using the map of the U.S. is a good idea, since it gives them a bit of geography as well, but you could also create a map of a fictional island or continent, and use that as well.  To make it even more interesting, you could have each student create their own map and system of equations, and then trade with a partner to solve.

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How does this topic extend what your students should have learned in previous courses?

If students have a firm understanding of inequalities as well as linear systems of equations, then they have all the pieces they need to understand linear systems of inequalities quite easily and effectively.  They know how to write an inequality, how to graph it on the coordinate plane, and how to shade in the correct region.  They also know the different processes whereby they can solve linear systems of equations, whether by graphing or by algebra.  The main difference they would need to see is that when solving a linear system of equations, their solution is a point, whereas with a linear system of inequalities, it is a region with many, possibly infinitely many, points that fit the parameters of the system.  It would be very easy to remind them of what they have learned before, possibly do a little review if need be, and then make the connection to systems of inequalities and show them that it is not something completely different, but is simply an extension of what they have learned before.

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How can technology be used effectively to engage students with this topic?

Graphing calculators are sufficiently effective when working with linear systems of equations, but when working with inequalities, they are rather limited in what they can help students visualize.  They can only do ≥, not just >, and have the same problem with <.  It is also difficult to see the regions if you have multiple inequalities because the screen has no color.  This link is an online graphing calculator that has several options for inequalities: https://www.desmos.com/calculator.  You can choose any inequality, <, >, ≤, or ≥, type in several equations or inequalities, and the regions show up on the graph in different colors, making it easier to find the solution region.  Another feature of the graphing calculator is that the equations or inequalities do not have to be in the form of y=.  You can type in something like 3x+2y<7 or solve for y and then type it in.  I would use this graphing calculator to help students visualize the systems of inequalities, and see the solution.  When working with more than two inequalities, I would add just one region at a time to the graph, which you can do in this graphing calculator by clicking the equation on or off, so the students could keep track of what was going on.


Live.Love.Laugh.Teach.  Blog by Mrs. Graves.  https://livelovelaughteach.wordpress.com/category/linear-inequalities/

Graphing calculator https://www.desmos.com/calculator





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