EGINNING A PROOF: Proving 2n-1 is Prime for all n

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brad sue
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Hi I have difficulty to begin with this problem:

prove or disapprove that 2n-1 is prime for all non negative integers n.

I know the definition of a prime number but how to apply it for this proof?

Please, can I have a suggestion to start this problem?

B
 
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Try some values of n and see if you can find a composite number (hint: I wouldn't be telling you to do this unless your search would end eventually).
 

Thread 'Finding the nth roots of a complex number'

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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