How Does Finite Dimensionality Affect the Spectrum in a Banach Algebra?

Tien
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Homework Statement



How to show element of finite dimensional banach algebra has finite spectrum?

Homework Equations



spectrum(x) = set of complex numbers 'c' with cI-x not invertible, I is identity

The Attempt at a Solution



please help to start, I don't know
 
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According to the rules of this forum, you have to show an effort at solving this before we can provide help.
 
Try showing that the eigenvalues belonging to different elements of the spectrum are linearly independent.
 
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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