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\chapter[Prove that $R$ is an equivalence relation on $\bbz$.]{Prove that $R$ is an equivalence relation on $\bbz$.}

Let $A = \bbz^2 - \{(0,0)\}$, and let $R$ be the relation on $A$ defined by 
\begin{align*}
R = \{((a,b), (c,d)) : ad-bc = 0\}.
\end{align*}
Prove that $R$ is an equivalence relation on $\bbz$, then describe the equivalence classes.

\section{First draft}
Due Friday, April 15 at 6:00 PM.

\begin{proof}

\end{proof}