# Which of the following integral domains are Euclidean domains

Which of the following integral domains are Euclidean domains?

1. $\mathbb{Z}[√(-3)]$
2. $\mathbb{Z}[x]$
3. $\mathbb{R}[x^2,x^3]=\{f=\sum_{i=0}^n a_ix^i\in\mathbb{R}[x]:a_1=0\}$
4. $(\mathbb{Z}[x]/(2,x))[y]$

How can we solve this problem. Can anyone suggest me something. Thanks

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To show that something is a ED, find a Euclidean function. To show thta something isn't, e.g show that it's not a PID. – Alex B. Dec 17 '12 at 9:12
@priti: Something is very strange in you definition of (3) – Dennis Gulko Dec 17 '12 at 9:26
@AlexB., ok if it works, but there are PIDs that are not Euclidean: en.wikipedia.org/wiki/Principal_ideal_domain#Properties – lhf Dec 17 '12 at 10:35

• $\mathbb{Z}[\sqrt{3}i]$ is not UFD because $(1+\sqrt{3}i)(1-\sqrt{3}i)=4=2.2$
• $\mathbb{Z}[x]$ is not PID because $(2,x)$ is not principal.
• Note that $x^2$ and $x^3$ are irreducible in $\mathbb{R}[x^2,x^3]$ and $(x^2)^3=x^6=(x^3)^2,$ hence it is not a UFD.
• $\mathbb{Z}[x]/(2,x)\cong\mathbb{F}_2$ which is a field, hence $\mathbb{F}_2[y]$ is ED.
Hence the correct option is the $4$th one.
 Most people denote the first ring by $\mathbb Z[i\sqrt{3}]$. – YACP Dec 17 '12 at 11:24