It is a thing I knew in the early 70s. I never got math and failed Algebra twice in HS before I dropped out and once in a CC. For that I was a failure, doomed to do some menial job. I joined the Marines and ended up doing Avionics/Electronics and retired from the field a few years ago. I needed applied learning, not general made up stuff.
THE POINT?

Helpful encouragement in math books is NOT a bad thing.
My brain isn't wired for math. I do know how to use resources though. Got calculator?
All support is appreciated and DeSantis can piss off!

I tried the googles but I doubt the meaning is correct.
I tried.
WTF does TDFG mean?
I do know TFG.
Thank you!