Derive formula for amount of monthly mortgage payment

[Denis]

It is essentially a generalization or clever manipulation (depending on how you look at it) of the so-called retrospective method for determining the outstanding liability just after any particular payment.
Had I not gotten used to obtaining the same results from spreadsheet amortization schedules, I might have come up with it in like a few years after retiring. If I might inquire with you: Did you perhaps learned it from a textbook? Or did you perhaps “discovered” it while you were still active in the workplace?

Gee Jonah, do you read minds? I retired in 2001!
I was a financial analyst with a large Credit Union up here: so had lots of opportunities to manipulate financial formulas.
You mentionned yourself and "the bottle"; haven't had a drink of alcohol since Apr 8/85 : and PROUD of it :idea:

 

[jonah]

Gee Jonah, do you read minds?

I wish I could. As you may have already guessed, I merely viewed your profile after stumbling across that neat "Denis" formula and being impressed by it.