On Friday, a quiet girl in my Algebra 2 class called me over and whispered something in my ear: "I can't remember how to plot a point." We needed to plot points to graph a line during our introduction unit/review on linear functions. She was embarrassed that by 11th grade she couldn't do this "easy" thing, but what she didn't know is that I see this every year.
Plotting points vs. slope: order matters
What is it about plotting a point that gives high school students so much trouble? I've given this a lot of thought in my 10 (gasp!) years teaching. Students learn how to plot points in 5th or 6th grade. Some time later, they learn slope.
Plotting points: x then y.
Slope: y then x.
Could this be it?
x is better than y. It just is.
Maybe it's something about x and y seeming to hold the same weight. I mean, they're both letters, right? Students may get confused that they travel along the x axis to find the x value but then up or down into shear space to find the y value. Why don't I travel along the y axis too? I've seen students do this.
Say they were trying to plot (-3, 5), they'd find -3 on the x axis, find 5 on the y axis, then have no idea what to do next because the points don't connect. By 11th grade, this could be a carryover from graphing Standard Form linear equations in 9th grade, but it's going to take me a few more years to figure this one out.
Say they were trying to plot (-3, 5), they'd find -3 on the x axis, find 5 on the y axis, then have no idea what to do next because the points don't connect. By 11th grade, this could be a carryover from graphing Standard Form linear equations in 9th grade, but it's going to take me a few more years to figure this one out.
The claw
I teach Special Education Math so followed one girl from Geometry to Algebra 2 to Consumer Math. In Geometry she couldn't plot a point. In Algebra 2 she couldn't plot a point.
Exasperated, I related plotting points to one of those claw machines that always take your money and don't give you a toy. She got it. I don't know how, but she did. Phew!
Exasperated, I related plotting points to one of those claw machines that always take your money and don't give you a toy. She got it. I don't know how, but she did. Phew!
This year's plan
This year I'm going to try something different. This year, I am going to flat out tell my students that x is better than y. I mean, it kind of is. Time stops for no one. x value. Enough said. Depending on where x is, y will be. x is the boss.
I'm going to draw a picture on the activeboard like the one you see in that photo above. I'll then highlight the entire thing yellow and only the x axis pink. I'll then highlight the x column of the table pink and the y column yellow, just like in the photo.
We'll travel along the pink x axis to find x first, then up into the yellow space to find y. This will both be a good visual for my students and also emphasize that we treat x and y completely differently. For x, we must travel on the x axis because it is the boss. For y we can travel up and down in space depending on what the y value is.
We'll travel along the pink x axis to find x first, then up into the yellow space to find y. This will both be a good visual for my students and also emphasize that we treat x and y completely differently. For x, we must travel on the x axis because it is the boss. For y we can travel up and down in space depending on what the y value is.
How do you teach this important topic that follows students for so many years?
Check out this coordinate plane math pennant activity for practice with plotting points.
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