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Right. It's magic. But once you have the machine... ----- Fundamental Theorem of Algebra: Every nonconstant polynomial over the complex numbers has a complex
by btilly 2y ago
Right. It's magic.
But once you have the machine...
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Fundamental Theorem of Algebra: Every nonconstant polynomial over the complex numbers has a complex root.
Proof: Suppose that p(z) is a polynomial over the complex numbers with no root.
Consider the function 1/p(z). If p(z) had no roots, then 1/p(z) is entire. But we can bound it for everything outside of a large circle because the leading term dominates the others. And since the large circle is compact, we can bound p(z) away from 0 inside the circle. Between the two, 1/p(z) is bounded, and so much be constant by Liouville's theorem.
But 1/p(z) is only constant if p(z) is constant. Therefore any complex polynomial with no complex roots must be constant.
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I'm convinced by the proof. But part of me still says that it is magic.