I have a very distinct memory of the quadratic formula: when my high school geometry teacher just assumed we all knew it, but most of the class had never seen

I have a very distinct memory of the quadratic formula: when my high school geometry teacher just assumed we all knew it, but most of the class had never seen it before. This sticks in my memory many, many years later because of the hours several of us spent (without being asked to do so) memorizing the thing, that being much easier than the version of the factorization method that we'd been taught previously. I did later learn about other methods (being curious about math, and having access to a much better Internet than during high school). Still, I don't think I'll ever forget that formula.