Question

show that the set of all n×n matrin under matrix addition form an abelion group
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Answer 1

Answer:

You can show that there is an element which does not have finite order, take for instance the matrix (10(n−1)×101×(n−1)0(n−1)×(n−1)).

Alternatively, you can see that each entry in the matrix is an element of R, so there are infinite choices for each entry.