| ∀ ay, a. (ax0 + ay)[a] = ay[a] ∨ a ∈ ax0 ⊦ ((p + ax0) + ay)[a] = ay[a] ∨ a ∈ p + ax0 |
∀ ay, a. (ax0 + ay)[a] = ay[a] ∨ a ∈ ax0 ⊦ ((p ' + ax0) + ay)[a] = ay[a], a ∈ p ', a ∈ ax0
Used simplifier rules: in-append: ⊦ a ∈ ax + ay ↔ a ∈ ax ∨ a ∈ ay;% ⊦ (ax + ax0) + ax1 = ax + ax0 + ax1;% ⊦ p + ax = p ' + ax;