Monday, October 19, 2009

Two Wrongs Make a Right

About an hour or so before class, a student emails me about one of the max-min problems on the WebAssign. I hadn't paid much attention to the function, and it turns out finding the critical numbers would require factoring a cubic -- without a greatest common factor of x. Now, I am old-school enough that I was raised in the era of the rational roots theorem and long division of polynomials, but this is the younger generation where all polynomials factor easily.

By coincidence, the first problem on today's Keynote slideshow for today was completely isomorphic. Even the constants were roughly the same. And the scenario of the word problem was the same. Pretty much the same problem. Had I actually done the problem ahead of time instead of just copying it from the textbook, I never would have put it on the slide. And the slides are posted on Blackboard pretty far in advance, so I can't really change my slideshows at the last minute.

So I used this as an opportunity to apologize for a problem that was harder than I had anticipated, and I showed them how to do it. With Wolfram Alpha. (I also pointed out that the WebAssign problem's answer was a modestly-sized whole number and they should feel free to just guess.) And then I promised them that none of the problems on the exam would be that tricky. I think that my project for Christmas break is to go over all of my slides and to take out the troublesome problems with messy answers.