| a ∈ a0 ' + rmdup(x0), ∀ a. a ∈ rmdup(x0) → a ∈ x0 ⊦ a = a0, a ∈ x0, a0 ∈ x0 |
a ∈ rmdup(x0), ∀ a. a ∈ rmdup(x0) → a ∈ x0 ⊦ a = a0, a0 ∈ x0, a ∈ x0
Used simplifier rules: a: ⊦ (x + y) + z = x + y + z; from specification list% ⊦ a ≠ b → (a ∈ b ' + x ↔ a ∈ x); (s)