# Homework Help: Units in a ring

1. Apr 16, 2010

### juniormint

1. The problem statement, all variables and given/known data
In the ring Z($$\sqrt{}5i$$) = n + m$$\sqrt{}5i$$, n and m integers, find the units.

2. Relevant equations

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3. The attempt at a solution
I know 1 and -1 are units, and my textbook seems to indicate that $$\sqrt{}5i$$ and -$$\sqrt{}5i$$ are also units, but I don't know if that's right because I don't know what the inverse of those elements would be -- multiplying them together gives you 5, right? Are there different units I haven't found?

thanks!