| a ∈ x0, a ∈ x ⊦ ∃ b, y, y0. b ∈ x ∧ x0 = y + b ' + y0 ∧ disj(x, y0) |
a ∈ a0 + x1, a ∈ x0, ∀ a, x0. a ∈ x0 ∧ a ∈ x1 → (∃ b, y, y0. b ∈ x1 ∧ x0 = y + b ' + y0 ∧ disj(x1, y0)) ⊦ ∃ b, y, y0. b ∈ a0 + x1 ∧ x0 = y + b ' + y0 ∧ disj(a0 + x1, y0)
Used simplifier rules: list freely generated by [], +;;% ⊦ ¬ a ∈ []; (s)