Nilpotent elements in a ring
Let
- Show that if
is nilpotent, then is a unit. - Give an example of a commutative ring with 1 that has no nonzero nilpotent elements, but is not an integral domain.
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Let $R$ be a commutative ring with 1. We say an element $n\in R$ is {\bfseries nilpotent} if there exists a number $k\in {\bf N}$ such that $n^k=0$.
\begin{enumerate}[label=\alph*)]
\item Show that if $n$ is nilpotent, then $1-n$ is a unit.
\item Give an example of a commutative ring with 1 that has no nonzero nilpotent elements, but is not an integral domain.
\end{enumerate}