Quintic equations cannot be solved algebraically in the general case. It would require more understanding of algebra by the program whereas I suspect this merely detects the order of the equation and then applies the proper solving formula (Abc for 2nd, Cardano for 3rd).

But nice work, it looks really professional for an out of hand learning project!

> I suspect this merely detects the order of the equation and then applies the proper solving formula (Abc for 2nd, Cardano for 3rd).

That's exactly right. You could build a quintic equation, but attempting to solve will return undefined.