I'm trying to find the roots of x^3 -2, I know that one of the roots are \sqrt[3] 2 and \sqrt[3] {2}e^{\frac{2\pi}{3}i} but I don't why.
The first one is easy to find, but the another two roots?
I need help
Thank you
Answer
If \omega^3 = 1 and x^3 = 2 then (\omega x)^3 = \omega^3 x^3 = 2.
Possible values of \omega are e^{\frac{1}{3}2 i \pi}, e^{\frac{2}{3}2 i \pi} and e^{\frac{3}{3}2 i \pi}. This is because 1 = e^{2 i \pi} = (e^{\frac{1}{k} 2 i \pi})^k.
So the solutions of x^3 - 2 = 0 are e^{\frac{1}{3}2 i \pi} \sqrt[3]{2}, e^{\frac{2}{3}2 i \pi} \sqrt[3]{2} and \sqrt[3]{2}.
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