| i ≠ 0, i = i0 / gcd(i0, j0) * gcd(i, j), j / gcd(i, j) = j0 / gcd(i0, j0), 0 < j, 0 < j0 ⊦ i * j0 = i0 * j, j = 0, i = 0, j0 = 0, i0 = 0 |
j / gcd(i, j) = j0 / gcd(i0, j0), i = i0 / gcd(i0, j0) * gcd(i, j), 0 < j0, 0 < j ⊦ i = 0, i0 = 0, j0 = 0, j = 0, i * j0 = i0 * j