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Semi Group - Printable Version

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Semi Group - elim - 09-14-2010 12:09 PM

(1) Show that semigroup $(S, \cdot)$ is a group if $\exists e_r \in S \; \forall a\in S \; \exists a_r^{-1}\in S \;(a\cdot e_r = a, \; a\cdot a_r^{-1} = e_r)$