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**mrpace****Member**- Registered: 2012-08-16
- Posts: 74

Z[√7] = {a+b√7|a.b ∈ Z}

2Z+iZ = {2a+bi|a,b ∈ Z}

Where C is the complex plane, Z is the set of real integers.

Any ideas? Thanks.

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**Olinguito****Member**- Registered: 2014-08-12
- Posts: 649

The first one.

The second one is not even a ring – it's not closed under multiplication.

*Bassaricyon neblina*

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