| ∀ n. (∀ n0. count(n0, (bag0 -- n) ++ n) = count(n0, bag0)) ↔ count(n, bag0) ≠ 0 ⊦ count(n, bag0) = 0, count(n0, (bag0 -- n) ++ m ++ n) = count(n0, bag0), n = m, n0 = m |
⊦ count(n, bag0 ++ n0) = (n = n0 ⊃ 1;0) + count(n, bag0)
∀ n. (∀ n0. count(n0, (bag0 -- n) ++ n) = count(n0, bag0)) ↔ count(n, bag0) ≠ 0 ⊦ (n0 = n ⊃ 1;0) + count(n0, (bag0 -- n) ++ m) = count(n0, bag0), count(n, bag0) = 0, n = m, n0 = m
Used terms: n, (bag0 -- n) ++ m, n0