# Help with creating an activity for graphing inequalities in two variables

I am new to CL, and not particularly good at it, so I’m having a hard time creating what I envision. I’d like to create an activity in which students choose a point, test it in an inequality, say y<=2x-3, and then plot a green (draggable) point if it works and a red (draggable) point if it doesn’t… Then show all the classes responses to notice that all the green dots are in one area (and hopefully zero in on errant mis-colored dots, understand the student error, then give students a chance to fix…) Then overlay the line y=2x-3 to show that all the points that work are on one side of the line. Rinse and repeat a few times, maybe with the 2nd time y<2x-3, and later x>4, y<5, etc on the x-y plane.

Is there anyone out there who has made a similar activity, or who could help me create such an activity?

I appreciate any help and/or redirection. Thank you.

Not exactly what you are trying to make but this contains some similiar ideas:
https://teacher.desmos.com/activitybuilder/custom/5c99328996ef52657be3d04b

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These slides focus on test points:
https://teacher.desmos.com/activitybuilder/custom/5ce9fedd454aac69f8f81dd3

Hey Alison!

Your vision can come to life in three steps! I’ll present them separately, but know that they can actually be done together once you get the hang of it:

Step 1: Plot the points from an input
https://teacher.desmos.com/activitybuilder/custom/5ced88e21df0500c65cc7e5c#preview/c94cf9b8-eb76-4e00-9d9d-8f32d3d434dd

Use parseOrderedPair to take a coordinate pair written in an input and put it into the graph. You can also use a table for this step but because you will be aggregating student data later, this method is encouraged.

Step 2: Make two copies of each point in the graph
https://teacher.desmos.com/activitybuilder/custom/5ced88e21df0500c65cc7e5c#preview/3d2e3ba8-970e-4c69-9142-6161530b5f82

Display each point based on whether or not they satisfy the desired inequality (in this case x+y>5)

Step 3: Aggregate Student Data
https://teacher.desmos.com/activitybuilder/custom/5ced88e21df0500c65cc7e5c#preview/301a660b-a5f7-47e5-9641-a47fdf5d6fe5

Use the aggregate function to collect each of the numbers from the students’ screen into a single list. Plot that list just like you plotted points on screen 2 by using conditions to hide and show points.

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Thank you SO much Jay. I am going to look at these links tonight and learn how to modify / optimize / these things for my own use.

While I was floundering around looking for how to do things this past weekend, I found another thread in the CL help area where some guy was apparently trying to do the same thing about a year ago, and you helped him out. I Googled the guy and found his blog and his activity. I thought it was pretty awesome, and wondered why something like it wasn’t a “featured” activity by Desmos!

Thank you again for helping. I adore Desmos, and want to keep learning how to use it better.

Alison Signorotti

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