[nhatcher]

Nice! This is my implementation:

https://github.com/ironcalc/IronCalc/blob/main/base/src/func...

although at this moment would only pass some "smoke" tests

RowZero is great!

[gamegoblin]

I started with basic Newton-Raphson solver too but found cases where it diverges but Excel somehow doesn't, so concluded that Excel has some kind of extra logic to handle more cases, so I also bolted on more fallback logic.