In this series, I’m compiling some of the quips and one-liners that I’ll use with my students to hopefully make my lessons more memorable for them.

One of my favorite pedagogical techniques is deliberating showing students a wrong way of solving a certain math problem, discussing why it’s the wrong way, and then salvaging the solution to construct the right way of doing the problem. I think this keeps students engaged in the lesson as opposed to learning a new technique by rote memorization.

Earlier in my teaching career, I noticed an unintended side-effect of this pedagogical technique. A student came to me for help in office hours because she couldn’t understand something that she had written in her notes. Lo and behold, she had written down the wrong way of doing the problem and had forgotten that it was the wrong way. Naturally, I clarified this for her.

This got me to thinking: I still would like to use this method of teaching from time to time, but I don’t want to cause misconceptions to arise because somebody was dutifully taking notes but didn’t mark that he/she was writing down an incorrect technique. So I came across the following one-liner that I now use whenever I’m about to start this technique:

Don’t write down what I’m about to say; it’s wrong.

Hopefully this prevents diligent students from taking bad notes as well as tips them off that they need to start paying attention to see where the logic went wrong and thus construct the proper technique.

I'm a Professor of Mathematics and a University Distinguished Teaching Professor at the University of North Texas. For eight years, I was co-director of Teach North Texas, UNT's program for preparing secondary teachers of mathematics and science.
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