| a ∈ butlastn(n, a0 ' + x), n ≤ # x + 1, ∀ a, n. a ∈ butlastn(n, x) ∧ n ≤ # x → a ∈ x ⊦ a = a0, a ∈ x |
⊦ n ≤ # x → butlastn(n, a ' + x) = a ' + butlastn(n, x)
¬ n ≤ # x, a ∈ butlastn(n, a0 ' + x), n ≤ # x + 1, ∀ a, n. a ∈ butlastn(n, x) ∧ n ≤ # x → a ∈ x ⊦ a = a0, a ∈ x
n ≤ # x, a ∈ a0 ' + butlastn(n, x), n ≤ # x + 1, ∀ a, n. a ∈ butlastn(n, x) ∧ n ≤ # x → a ∈ x ⊦ a = a0, a ∈ x
Used terms: x, a0, n