I scribbled this in the margin of a test I took the other day

A couple of hours ago I would have sworn that I knew and understood the algorithmic approach to changing the base in a difference equation. It’s unfortunate that tests, while great for establishing application of a memorized algorithm, do so little to show understanding and internalization of the concepts which that regurgitated problem solving strategy actually represents.

a.k.a. no matter how much I fiddle with the terms, it appears that I have forgotten the formula :-(