⊦ 0 ≤ i → ¬ (i + 1) * (i + 2) ≤ 0
0 ≤ i + j - 1 → ¬ ((i + j - 1) + 1) * ((i + j - 1) + 2) ≤ 0 ⊦ 0 ≤ j ∧ 0 ≤ i → ¬ (i + j) * (i + j + 1) < 0
Used terms: i + j - 1