Graphing Linear, Quadratic, and Exponential Models*

Using Desmos Activity Builder to Talk About Student Work


What do you notice about this student’s thinking? What do you wonder about it?

I made a little Desmos activity to see if it’s possible to use their activity builder to share and comment on student work. I asked people to circle something they noticed in this student’s work. Here is the overlay showing everything that everyone circled.


I’m not sure what to make of all that overlaid, but I’m definitely interested. The written answers people offered were also really interesting. Here is a sampling:

Guest: “This is a common error for my students as well. They  do not recognize that this is a quadratic function and try to get a straight line.”

Kevin: “These don’t seem to be in any particular order.”

Lane: “Does he have an eraser? Does he get confused calculating with zero?  Does he know the shape of a parabola?  Does he know that a function cannot possible have one point on top of another? Does he sometimes get confused with x^2 and 2x?  Could he have analyzed his own mistakes with a calculator?  By not checking with a calculator will some of his errors snowball and cause further confusion?  Is the student feeling frustrated? I think it is good this student understands the choice of input does not have to be in a particular order.”

Jonathan: “I notice that there is a disconnect in the student’s knowledge of linear vs. quadratic equations. I wonder how come the student did not use any negative values in her table.”

While there were a lot of great observations, the one that stood out to me was that this student could probably learn to recognize that this sort of equation will produce a U shape. Knowing that this sort of equation produces a U will make it more likely that they will test negative x-values, or at least more reliably guess the rest of the shape. I agree: it seems as if this student is trying to fit a U-shaped function into a line-shaped paradigm.

What activity could we design that would help students like this one develop their thinking?

Inspired by Bridget, I put this together:

Response to Mistake Templates - Graphing y = x^2 - 4

In the Desmos activity, I asked if people could think of a way to improve my rough draft. Here were three responses that represent some of the variations people had:

pic6 pic5 pic4

On twitter, Bridget had a second idea for an activity that would help students like this one develop their thoughts.

To wrap things up, I shared a mockup of Bridget’s alternative activity and asked people what they thought about it.


Some selected responses:

Max: I prefer my version of the previous activity — this activity doesn’t invite students to consider why the parabola is symmetric — it’s easy enough to connect the linear and nonlinear representations and not confront the whys of the symmetry of the nonlinear representation. Maybe including y = x^3 + 4 as a third example (with both graph and equation provided) would support that sense-making?

Brian: I like the idea of having one more equation than graph. I’m also wondering about the choice to have two linear functions vs. one quadratic. This activity provides less structure than the previous since, to determine what the function’s graph looks like he would need to do it himself. The other provided the Desmos graph. On the other hand, this activity does provide the student with a more possibilities of visualizing the function, which could yield insight into how he’s thinking about the quadratic function.

Bridget: I wonder if the graphs should be discrete points instead of continuous. Not sure if it would make a difference or not. I also wonder if the missing representation should be another quadratic. I’m trying to consider if the connecting representations should include tables. I’m not sure…

Also, I think the previous slides connect more to the issue at hand. On an assessment-do you think this student could be given the equation y=x^2-3 and choose the correct graph from four multiple choice? I’m not sure…

Overall, this was fun! I’m excited to try it again.

Geometry Graphing

Plotting Points

andy1 andy2


Thanks to Andy Zsiga for the submissions. He’s wondering whether anyone has perspective on why students would graph several points correctly, and then mess up the point that contains a zero as one of its coordinates.

Anyone have a theory?

Functions Graphing Interpreting Functions Uncategorized

A Contest!


Marshall Thompson is offering a substantial bounty for the correct explanation for this mistake. (He knows the truth from talking to the student.)

Who’s got it?

Graphing Interpreting Functions

Graphing Stories



What does this question reveal about the student’s understanding?

(Also: do you agree with the mark given by the teacher?)

Algebra 1 Graphing High School: Functions Linear, Quadratic, and Exponential Models*

Graphing Equations

graphing mistake

Three points to you if you can convincingly explain where “x = 2” comes from.

Graphing Interpreting Functions

Impossible Graphs

IMG_2584 IMG_2586

How would you mark these problems? What do the kids understand? What don’t they?

Graphing High School: Modeling linear functions Linear, Quadratic, and Exponential Models*

Linear Modeling and Graphing

What’s the mistake? How would you help?

Thanks to John Weisenfeld for the submission.

Graphing Linear, Quadratic, and Exponential Models* Quadratics

Axis of symmetry and vertex

What does this mistake reveal about the kid’s thinking? How would you take the kid’s thinking to the next level?

F-IF.7 Graphing

“Can’t graph it. Too big a line.”

“The line’s too big.” So what? Why does this matter to the student, and what does this reveal about his understanding of graphing?