Negative numbers are not primes, although one could certainly argue that they should be.  But I'm not about to go and change the basic framework of math.

Yes i cant use negative numbers and -5-2 is -7 but if your trying to say -2+5 it would only equal3.

It's not possible, and here is a simple proof to show why:

All prime numbers except 2 are odd.

Case 1: One of the prime numbers is 2:

If one of the prime numbers is 2, the other must be 9, which is not a prime number.

Case 2: Neither of the prime numbers is 2:

Then both prime numbers are odd.  Let x and y be odd numbers.  Then x = 2k + 1 for any integer k (ignoring the restriction for primeness) and y = 2l + 1 for any integer l.

Then x - y = 2k + 1 - (2l + 1) = 2k - 2l = 2(k - 1).  Since k - l is an integer, 2(k - l) is an even integer, and thus not 7.

Therefore the are no two prime numbers such that p1 - p2 = 7.  QED.

Does anyone know what 2 prime numbers subtracted together that equals 7?


like this:               7= prime - prime