I am having trouble figuring out how to prove this:
If $p$ is a prime not equal to $2$ nor $5$, and $n$ is any integer, show that $p$ must be of the form $5k+1$ or $5k+4$ if $p \mid (n^2 - 5)$.
Any help is greatly appreciated!
I am having trouble figuring out how to prove this:
If $p$ is a prime not equal to $2$ nor $5$, and $n$ is any integer, show that $p$ must be of the form $5k+1$ or $5k+4$ if $p \mid (n^2 - 5)$.
Any help is greatly appreciated!