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