1. divisible by 24

if n is a prime number greater than 6, then prove that n^2-1 will be divisible by 24.

2. Recently this topic has been treated here...

http://www.mathhelpforum.com/math-he...er-theory.html

If p is an odd number grater than 5 non multiple of 3, p^2-1 is divisible by 24...

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$\chi$ $\sigma$

3. Consider the fact that $n^2-1=(n+1)(n-1)$. Now consider the divisibility of $n+1$ and $n-1$ by 3, 2, and 4, using the fact that n is a prime greater than 3, and so is odd and not divisible by 3.

--Kevin C.