I came across this question while reading quadratic equations ? $3i$ which can be expressed as $\sqrt{-9}$ will be a positive or a negative number ?
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2Someone told you yesterday in the comments to this qusetion that there is no sensible notion of order on the complex numbers... discussing their positivity and negativity amounts to the same thing. – rschwieb Mar 10 '21 at 14:58
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Does this answer your question? Ordering on complex numbers – hardmath Mar 11 '21 at 18:49
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$3i$ is a complex number that is not a real number, so it's neither positive nor negative. Positive numbers have argument $0$ and negative numbers have argument $\pi$, whereas $\operatorname{Arg}(3i)=\frac\pi2$.
Karl
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@TheNerd Positivity & negativity refers only to numbers on the real line, not general complex numbers on the real-imaginary (complex) plane. – ryang Mar 10 '21 at 06:44