Let be a prime number , with . What is the greatest integer such that all have a remainder of 1 when divided by ?
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
Since p 2 has a remainder of 1 when divided by x , then x ∣ p 2 − 1 . p 2 − 1 = ( p − 1 ) ∗ ( p + 1 ) . p is prime, so it is odd, given that the only even prime number is 2 and p > 3 , so p − 1 and p + 1 are even, and because they're consecutive even numbers, one of them is a multiple of 4 . Also, p , p − 1 and p + 1 are 3 consecutive integers, so one of them is a multiple of 3 and it can't be p because it is prime and greater than 3 . Therefore 2 ∗ 4 ∗ 3 ∣ p 2 − 1 . So the answer is 2 4