that N(ry) = N(x)N(y) for all x and y in 22). 2. If x is invertible in Z[1], show that N(x) must equal 1. 3. Conclude that the only units of Z are ±1 and ±.

Advanced Engineering Mathematics
10th Edition
ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
Chapter2: Second-order Linear Odes
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abstract algebra

**Exercise 2.113**

This exercise determines the units of the ring \( \mathbb{Z}[i] \):

1. Define a function \( N : \mathbb{Z}[i] \to \mathbb{Z} \) by \( N(a + bi) = a^2 + b^2 \). Show

(There are no graphs or diagrams in this image.)
Transcribed Image Text:**Exercise 2.113** This exercise determines the units of the ring \( \mathbb{Z}[i] \): 1. Define a function \( N : \mathbb{Z}[i] \to \mathbb{Z} \) by \( N(a + bi) = a^2 + b^2 \). Show (There are no graphs or diagrams in this image.)
1. Prove that \( N(xy) = N(x)N(y) \) for all \( x \) and \( y \) in \( \mathbb{Z}[i] \).

2. If \( x \) is invertible in \( \mathbb{Z}[i] \), show that \( N(x) \) must equal 1.

3. Conclude that the only units of \( \mathbb{Z}[i] \) are \(\pm 1\) and \(\pm i\).
Transcribed Image Text:1. Prove that \( N(xy) = N(x)N(y) \) for all \( x \) and \( y \) in \( \mathbb{Z}[i] \). 2. If \( x \) is invertible in \( \mathbb{Z}[i] \), show that \( N(x) \) must equal 1. 3. Conclude that the only units of \( \mathbb{Z}[i] \) are \(\pm 1\) and \(\pm i\).
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