How are valid/Invalid forms useful?

BetterCallSaulAndNotMe

I was doing great with this course so far. However, when i got to memorizing the invalid and valid forms. I got really confused.
First of, we dont have any sample LSAT questions where this could be applied.
I still dont understand, how is this useful in the actual LSAT? Is it actually worth taking hours to memorize??

Matt Sorr

The valid and invalid forms are mostly useful with LR questions that rely heavily on formal logic (often questions like parallel method of reasoning or flaw). I believe later in the CC, not long after learning the forms, you’ll go over some questions that use them.

WinningHere

J.Y. Also deciphers them on harder questions to get to the correct answer.