It looks like an alternating series, so It’s likely from a physics class involving electrostatic or maybe control systems. It also could be from a later calculus class where you’re first introduced to alternating series like Taylor or Leibniz.

I haven’t figured out how to login using Jerboa. There’s no option for me.

Use googles cached option.

You don’t need the /s we all know you’re being sarcastic.

Tried them all. Lemmy made more sense.