Let A be a ring with and K be the set { }. 1) If then is invertible and 2) If \ {0,1} then A is isomorphic with or .
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Just to start you off on this, if then , .
Originally Posted by petter Let A be a ring with and K be the set { }. 2) If \ {0,1} then A is isomorphic with or . suppose so thus: hence in order to prove that we only need to show that so suppose so call this now since we also have: which gives us: and give us: i.e. contradiction! Q.E.D.
Last edited by NonCommAlg; Jan 5th 2009 at 05:31 AM.
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