“Well, there are all sorts of formulas in junior high school math: Pythagoras’s theorem, the quadratic equation, that sort of thing … Memorizing formulas enables you to solve a whole variety of problems. If, however, you memorize a formula wrongly to start with, you’ll end up getting things wrong over and over again. That can happen, can’t it? … Make sure to get your students to memorize all the formulas correctly.”