4. Suppose d € Z with d > 1. This ensures that √-d & Q. Prove that Z[√-d]× = {±1}. (Hint: use the norm.)

Advanced Engineering Mathematics
10th Edition
ISBN:9780470458365
Author:Erwin Kreyszig
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Chapter2: Second-order Linear Odes
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4. Suppose d € Z with d > 1. This ensures that √-d & Q. Prove that Z[√=d]× = {±1}.
(Hint: use the norm.)
An integral domain R is said to have unique factorization if the following two conditions,
which correspond to the existence and uniqueness of prime factorizations, respectively, hold:
(U1) each nonzero, nonunit element of R is a product of one or more primes; and
(U2) if p₁, P2,..., Pm and 91, 92, ..., qn are primes such that
P1P2 Pm 9192 qn,
then m = n and there are units u₁, U2,..., um in R such that, after possibly reindexing, we
have pi= uigi for 1 ≤ i ≤m.
Transcribed Image Text:4. Suppose d € Z with d > 1. This ensures that √-d & Q. Prove that Z[√=d]× = {±1}. (Hint: use the norm.) An integral domain R is said to have unique factorization if the following two conditions, which correspond to the existence and uniqueness of prime factorizations, respectively, hold: (U1) each nonzero, nonunit element of R is a product of one or more primes; and (U2) if p₁, P2,..., Pm and 91, 92, ..., qn are primes such that P1P2 Pm 9192 qn, then m = n and there are units u₁, U2,..., um in R such that, after possibly reindexing, we have pi= uigi for 1 ≤ i ≤m.
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