| ∀ a, bag1. count(a, bag ∪ bag1) = count(a, bag) + count(a, bag1) ⊦ count(a, (bag ∪ bag1) ++ a0) = count(a, bag ++ a0) + count(a, bag1) |
⊦ a ≠ b → count(a, bag ++ b) = count(a, bag)
a = a0, ∀ a, bag1. count(a, bag ∪ bag1) = count(a, bag) + count(a, bag1) ⊦ count(a, (bag ∪ bag1) ++ a0) = count(a, bag ++ a0) + count(a, bag1)
∀ a, bag1. count(a, bag ∪ bag1) = count(a, bag) + count(a, bag1) ⊦ a = a0, count(a, bag ∪ bag1) = count(a, bag ++ a0) + count(a, bag1)
Used terms: a0, bag ∪ bag1, a