Way to show x^n + y^n = z^n factorises as (x+y)(x+psi y)⋯(x+psi^(n-1) n−1y)=z^n

jastukudYb

jastukudYb

Answered question

2022-11-23

Way to show x n + y n = z n factorises as ( x + y ) ( x + ζ y ) ( x + ζ n 1 y ) = z n

Answer & Explanation

Aleah Rowe

Aleah Rowe

Beginner2022-11-24Added 15 answers

We will make use of the following theorem
Theorem: Let P ( x ) be a polynomial and P ( z ) = 0, then x z divides P ( x )
Let n be odd and write
P ( x ) = x n + y n ,
then P ( ζ r y ) = 0 for all n powers of r.
Therefore ( x + y ) ( x + ζ y ) ( x + ζ 2 y ) divides P(x) but it has the same degree so its equal (up to a constant factor which is easily seen to be 1).

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