[doodlebugging]

I just went through the Internet Archive's issues of MacWorld from back in the day and think I found the software.

On page 9 (10 in the archive) of the April 1988 issue there is an advert for Eureka: The Solver by Borland International (Of course! They had such excellent software for years.)

There is a writeup about it on pages 191-192 (pages 192-193 in the archive).

One of the tools available is a polynomial finder. That is the tool that I used.

I will look around to see whether I still have the disk.