| ∃ d, ay, az. ax = ay + (a × d)' + az ⊦ ∃ d. a × d ∈ ax |
⊦ ∃ d0. a × d0 ∈ ay ∨ a × d0 = a × d ∨ a × d0 ∈ az
Used simplifier rules: a: ⊦ (ax + ax0) + ax1 = ax + ax0 + ax1; from specification list[assoclist]% ⊦ p ∈ p0 ' ↔ p = p0; (s)% ⊦ p ∈ ax + ax0 ↔ p ∈ ax ∨ p ∈ ax0; (s)