| a ∈ x0, ∀ a, b. a ∈ x0 → a = b ∨ a ∈ x0 -l b ⊦ a = b, a = a0, a ∈ (a0 ' + x0) -l b |
b = a0, a ∈ x0, ∀ a, b. a ∈ x0 → a = b ∨ a ∈ x0 -l b ⊦ a = b, a = a0, a ∈ (a0 ' + x0) -l b
a ∈ x0, ∀ a, b. a ∈ x0 → a = b ∨ a ∈ x0 -l b ⊦ b = a0, a = b, a = a0, a ∈ (a0 ' + x0) -l b
Used formulas: b = a0