⊦ i + j = 0 ↔ i = ~ j
0 ≤ gcd(i0, j0), gcd(i, j) = ~ gcd(i0, j0), 0 < gcd(i, j) ⊦ gcd(i, j) = 0
Used terms: gcd(i0, j0), gcd(i, j)