| a ≠ a0, ∀ a, y. x0 \ (a ' + y) = (x0 -l a) \ y, a0 = a ∨ a0 ∈ y ⊦ x0 \ (a ' + y) = (a0 ' + (x0 -l a)) \ y |
a0 ∈ y, ∀ a, y. x0 \ (a ' + y) = (x0 -l a) \ y ⊦ a = a0, x0 \ (a ' + y) = (x0 -l a) \ y
Used simplifier rules: diff-y: ⊦ a ∈ y → (a ' + x) \ y = x \ y;%a: ⊦ (x + y) + z = x + y + z; from specification list