| a ' + x = y + b ' ⊦ x = [], a ∈ y ∧ b ∈ x |
b ' + x = y + b ', b ∈ x ⊦ x = [], b ∈ y
Used simplifier rules: in-14: ⊦ a ' + x = y → a ∈ y;%a: ⊦ (x + y) + z = x + y + z;%in-15: ⊦ x + a ' = y → a ∈ y;%in-append: ⊦ a ∈ x + y ↔ a ∈ x ∨ a ∈ y;%in-17: ⊦ a ∈ b ' ↔ a = b;%ni: ⊦ x + a ' = y + z ∧ ¬ a ∈ z → z = [];