THEOREM 1:
(a) Let p and q be natural numbers, with p a prime. Then, the diophantine equation
1 2
1 1
p x x
q = + has a solution in the set of natural numbers N , with 1 x and 2 x distinct, if and
only if p +1 ≡ 0(mod q). If the above equation is solvable, then the solution is uniquely
determined (up to symmetry) and given by
q
x p 1
1
+
= and ⎟
⎟⎠
⎞
⎜ ⎜⎝
⎛ +
=
q
x p p 1
2 .