Let p be a rational prime.¹ (a) Prove that p factors nontrivially (i.e., does not stay prime) in Z[i] if and only if there are integers a and b such that p = a² +6². (Hint: what must the norm of a nonunit factor of p in Z[i] be?) (b) Deduce from (a) that, if p factors nontrivially in Z[i], then p = 2 or p = 1 (mod 4). (Hint: for odd p, use part (b) of the previous problem.)

Algebra & Trigonometry with Analytic Geometry
13th Edition
ISBN:9781133382119
Author:Swokowski
Publisher:Swokowski
Chapter4: Polynomial And Rational Functions
Section4.2: Properties Of Division
Problem 52E
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4. Let p be a rational prime.¹
(a) Prove that p factors nontrivially (i.e., does not stay prime) in Z[i] if and only if there
are integers a and b such that p = a² + b². (Hint: what must the norm of a nonunit
factor of p in Z[i] be?)
(b) Deduce from (a) that, if p factors nontrivially in Z[i], then p = 2 or p = 1 (mod 4).
(Hint: for odd p, use part (b) of the previous problem.)
Transcribed Image Text:4. Let p be a rational prime.¹ (a) Prove that p factors nontrivially (i.e., does not stay prime) in Z[i] if and only if there are integers a and b such that p = a² + b². (Hint: what must the norm of a nonunit factor of p in Z[i] be?) (b) Deduce from (a) that, if p factors nontrivially in Z[i], then p = 2 or p = 1 (mod 4). (Hint: for odd p, use part (b) of the previous problem.)
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