3(mod 4) x
p . Thus, x is odd, then 2(mod5) x
p or 3(mod5) x
p . Since 5 0(mod5)
y
, it follows
that 2
z 2(mod5) or
2
z 3(mod5) . This is a contradiction.
Therefore, by case 1 and 2, the Diophantine equations 2
5
x y
p z has no non-negative integer
solution if p 3(mod 4) and p 2(mod5).
Theorem 3.4 The Diophantine equations 2
5
x y
p z where p 3(mod 4) and p 3(mod5), has
no non-negative integer solution.
Proof. Let p be prime number and x, y and z be non-negative integer solutions of 2
5
x y
p z
Suppose p 3(mod 4) and p 3(mod5).
Case 1: If x or y is zero, then by Lemma 2.2 the Diophantine equations 2
5
x y
p z has no positive
integer solution. On the other hand, the case z 0 is obviously not possible. Hence, these equations have no
non-negative integer solution.
Case 2: Let x 1 and y 1. Similarly prove to the case 2 in Theorem 3.2 we conclude that the
Diophantine equations 2
5
x y
p z has no non-negative integer solution if p 3(mod 4) and p 3(mod5)
Therefore, by case 1 and 2, the Diophantine equations 2
5
x y
p z has no non-negative integer
solution if p 3(mod 4) and p 3(mod5).