| 0 < i, 0 < j, j ≤ i, 0 ≤ j, 0 ≤ i ⊦ fac(i - j) * j * fac(j - 1) = fac(j) * fac(i - j), i * fac(i - 1) / (fac(i - j) * fac(j - 1)) = j * fac(i) / (fac(i - j) * j * fac(j - 1)), fac(i - j) * j * fac(j - 1) | fac(i) |
⊦ 0 < i → fac(i) = i * fac(i - 1)
Used simplifier rules: associativity: ⊦ i * j * j0 = (i * j) * j0; from specification int-mult%commutativity: ⊦ i * j = j * i; from specification int-mult Used terms: j