Question

If I'm presenting the solution to something in a PowerPoint and the solution method is really long, how much should I include?

Answer 1

> it's a full page and a half on paper

That's hardly "super long". Plenty of solutions to problems are way longer. What academic level are you aiming for, OP?

Answer 2

Depends on the solution itself. You don't always have to go from A to Z, it might help to give an idea why Z makes sense, and what the challenge or idea is to prove this.

Answer 3

Are you going to be discussing the details of the solution method? If not you can probably represent most intermediate steps as simplified descriptions of what was done, and leave the detail in an appendix at the end for those that are interested.