Lemma 2.3. (3,3) is a unique solution ( y, z) for the Diophantine equation
1+ 2y = z2 where y and z are non-negative integer.
Proof: Let y and z be non-negative integers such that 1+ 2y = z2 . If
y = 0 , then z2 = 2 which is impossible. Hence, y ≥1. We can consider as
follows:
Case y =1: We have z2 = 3 which is impossible.
Case y > 1: We have z2 − 2y =1. By Proposition 2.1, we have y = 3
and z = 3 .
Hence, the solution (3,3) is a unique solution ( y, z) for the Diophantine equation
z2 − 2y =1.