/sci/ - Science & Math

>>7972503

Happily, my mistake is easily identified upon review of the above. Between two posts, I started consistently replacing the correct "5727" term from >>7972063 , with the incorrect "5257", which was then reproduced consistently throughout >>7972292
>>7972338 and >>7972503 . Upon double checking, the rest of what I did still looks right to me. Especially since I can now plug in the corrected C+ and C- (replace per the above), and end up with this, which agrees with the earlier "solver". The imaginary parts in this case still cancel nicely.

So I'm satisfied that I have used the formula >>7970829 , together with appropriate choices of ks in the De Moivre representation earlier, to arrive at a closed-form representation one of OP's three roots (pic related). Specifically, the single negative one among its three distinct real roots.