Every nxn matrix can be written as a linear combination of matrices in GL(n,F)

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Homework Statement


Prove: Every nxn matrix can be written as a linear combination of matrices in GL(n,F).


Homework Equations


GL(n,F) = the set of all nxn invertible matrices over the field F together with the operation of matrix multiplication.


The Attempt at a Solution


I know all matrices in GL(n,F) are invertible and hence have linearly independent columns and rows. I was thinking perhaps there is something about the joint bases for the n-dimensional column and row spaces, respectively, that could provide a basis for M_{nxn}(F), which has dimension of n^2. But I'm not really sure if that works.
 
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Okay, I figured it out. Nevermind (although once a post gets buried two screens back, it's not likely to be answered anyway, even if it has zero replies...).
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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