Solving the TVM equation for the interest rate

[Gamo]

I was wondering on how HP doing this TVM on finding the interest [i] also.
I'm happen to read more about this in HP Journal Issue October 1977 start from page 22 in the article state that the previous HP-80 Financial Calculator used 3 separate TVM formula which their performance deteriorated unacceptably when they were applied to the new more general equation. On the newer desktop model the HP-92 used better general equation using one formula all together and did work out very well.

This topic is very complicated for me and I like to share this information to anyone who like to know about this especially to Dieter.

I try to implement this single TVM equation into the Newton's Method program by using Register as their TVM variables like STO 1 for [n] STO 2 for [I] and so on and not working yet.


Link to this HP Journal: https://www.dropbox.com/s/6beqloidryfdim...7.pdf?dl=0

Gamo