Proof by Contraposition/Examples

Examples of Proof by Contraposition

If $2^n - 1$ is Prime then $n$ is Prime

An example of a proof by contraposition would be as follows:

Let $2^n - 1$ be prime.
Then $n$ is prime.


This is proved by showing that:

If $n$ is composite, then $2^n - 1$ is composite.
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