simp at *
case intro
rel_sub : ∀ x ∈ {p | p.1 + 3 * p.2 = 4}, x ∈ Set.univ ×ˢ Set.univ
rel_uniq : ∀ (x : ℤ), ∃! y, (x, y) ∈ {p | p.1 + 3 * p.2 = 4}
⊢ False
case intro
rel_uniq : ∀ (x : ℤ), ∃! y, x + 3 * y = 4
rel_sub : True
⊢ False