j1 = i0 +1, ∀ i, j. i * (j + j1) = i * j + i * j1 ⊦ i * (j + j1)-1 = i * j + i * i0
Used simplifier rules: ⊦ i = j -1 ↔ j = i +1; (elim) Used terms: j1, i0