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# factorizing over Q watch

1. How do i factorize polynomials like
x^9 + 1 ans x^16 +1 over Q?

I have the formua: x^2n - 1 = (x^n -1)(x^n +1)
But i don't know what to do after that?
2. In what context are you factorising the polynomial?

If you're after the roots of the thing, then if you know about complex numbers you can find them (similar to the roots of unity) and if they're rational you've found rational factors.

If you're studying ring theory then you'll want to use a pretty important theorem about irreducible polynomials over Z and Q.

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