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In Wikipedia it says that "A $n\times n$ matrix of a ring $R$ is commutative if and only if $n=1$ and $R$ is commutative". Could someone please provide me with a proof/reference to a proof of that ?

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    Hint: All you need is to find two $2\times 2$ matrices that do not commute.2012-12-08
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    http://groupprops.subwiki.org/wiki/Center_of_general_linear_group_is_group_of_scalar_matrices_over_center2012-12-08
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    I cannot find your exact quote there. How is a single matrix commutative?2012-12-08

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