Last week I told my Precalculus class that they would be haunted, haunted by a common algebraic mistake. A visual depiction can be found below.
I almost never purposely put an incorrect statement in the notes. I know that whatever I write, right or wrong, goes into students’ brains and I have no control about comes out. I just hate to say, “Don’t do this.” It just emphasizes the wrong instead of encouraging the right. With that disclaimer, take a look.