| a ∈ y, a ∈ (a0 ' + x0) \ y, ∀ a1, y0. ¬ a1 ∈ x0 \ y0 ∨ ¬ a1 ∈ y0 ⊦ a0 ∈ y |
a ∈ y, a ∈ x0 \ y, ∀ a1, y0. ¬ a1 ∈ x0 \ y0 ∨ ¬ a1 ∈ y0 ⊦ a0 ∈ y
Used simplifier rules: diff-n: ⊦ ¬ a ∈ y → (a ' + x) \ y = a + (x \ y);%in-rec: ⊦ a ∈ b ' + x ↔ ¬ ¬(a = b ∨ a ∈ x); from specification list%a: ⊦ (x + y) + z = x + y + z; from specification list%c: ⊦ a + x = a ' + x; from specification list