On mathworld's discussion of the cubic formula he has that(adsbygoogle = window.adsbygoogle || []).push({});

"determining which roots are real and which are complex can be accomplished by noting that if the polynomial discriminant D > 0, one root is real and two are complex conjugates; if D = 0, all roots are real and at least two are equal; and if D < 0, all roots are real and unequal."

Does that sound wrong to anyone else? It's been a while since I learned about cubic discriminants but doesn't a negative discriminant mean two complex roots?

I had actually forgotten what a negative cubic discriminant meant so I was looking it up but this seems wrong to me. Anybody feel confident one way or the other?

Thanks,

Steven

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# Discriminant of a cubic

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