What does the student have right, and what does the student have wrong? How would you help?
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Category: Algebra 1
What makes this idea so attractive to students? Why should it be true that 
What is this student thinking? It’s a bit tricky, so extra points if you come up with a complete story that includes a list of things that we know that this kid knows.
From the student’s work, what can we infer that the student knows? What is the student thinking? How would you help?
What aspect of solving linear equations is this student struggling with? From the student’s point of view, why does the moves made seem like the right ones?
Are there any interesting things that you do to help students with linear equations? How do you make the right moves seem intuitive?
Today’s mistake is a classic, at least in my classroom. What makes this mistake so tempting for students, and how do you help them see the light?
The mistake is pretty easy. But what’s the underlying misconception?
Today’s submitter asked the following question:
Here are a selection of student responses:
- Slope is how far apart the two points are. You can use the idea of rise over run. You rise a certain amount and then run right or left depending ona negative or positive.
- Slope is how you measure two or more points or equations on a graph.
- It’s the y-intercept divided by the x intercept and intercept is the coordinates.
- Slope is the change in the dependent (which can be anything) over the independent (which can be anything).
- Slope is one point of a line on a graph minus another point on the same line in that graph.
- The slope is the difference of the dependent variable (y) over the independent variable (x).
- Slope is the rate of change between the dependent and the independent. If the dependent went up by 2 every time x, the independent, went up by 1, then the slope would be y over x which in this case is 2.
- Slope is when you take one point on a graph and a second one and see the difference between them and the numbers whatever y go over the numbers of the difference of x and that’s your answer.
- Slope is the rate of change in an equation, graph or story. For example, 2x -4 = y, take two possible solutions the rate of change is 2.
- Slope is the unit that you “go up by”. Let’s say you buy 4 apples for $4. The slope is 1 because it always goes up by one, 6 apples would be $5.
- Slope is the rate of change in an equation.
- The rate of change, between an independent and depending things.
- You have two points so all you do is see how far apart they are. We see that it goes from (4, 2) to (2,1) so it’s 2/1.
- Slope shows how a number increases or decreases and by how much.
- A slope is the change of rate in a problem for example, a man gets paid $5 an hour How much does he get after working for 3 hours? He gets $15, so 5 is the slope.
- Slope is when you have 2 numbers and find out what the answer will be.
There’s a lot to work on here. In the comments, pick a student and dig into their understanding of slope. And also, can you infer what the approach of the unit was from the students’ responses? How could the unit be improved?
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Quadratics Quiz
As we start a new week of Math Mistakes, if you have any pictures of student work that you find interesting in any way, please send it in.
Today’s student has a couple of ideas worth drawing out. Do so in the comments.
What does this kid think “factoring” means? And, at least to me, the more interesting question is: where did that conception of “factoring” come from? Tease it out in the comments.