| (i0 + j0) * (i0 + j0 + 1) = i1 * 2, (i + j) * (i + j + 1) = (i1 + j0) * 2 - j * 2, j ≤ i1 + j0, 0 ≤ i1 + j0, 0 ≤ i, 0 ≤ j, 0 ≤ i0, 0 ≤ j0, 0 ≤ i1 ⊦ i = i0 ∧ j = j0 |
⊦ (i + i0) * j = i * j + i0 * j
(i0 + j0) * (i0 + j0 + 1) = i1 * 2, (i + j) * (i + j + 1) = i1 * 2 + j0 * 2 - j * 2, j ≤ i1 + j0, 0 ≤ i1 + j0, 0 ≤ i, 0 ≤ j, 0 ≤ i0, 0 ≤ j0, 0 ≤ i1 ⊦ i = i0 ∧ j = j0
Used terms: 2, j0, i1