∃ m0. 2 * m0 = m * n ⊦ ∃ m0. 2 * m0 = m, ∃ m0. 2 * m0 = n
(∃ m0. 2 * m0 = m) ∨ (∃ m0. 2 * m0 = n) ⊦ ∃ m0. 2 * m0 = m * n