constructor
case mpr
x : ℕ
mem : x ∈ Set.singleton 0
i : ℕ
mem' : x = 0
⊢ x ≤ 2 * i ∧ Even x
case mpr.left
x : ℕ
mem : x ∈ Set.singleton 0
i : ℕ
mem' : x = 0
⊢ x ≤ 2 * i

case mpr.right
x : ℕ
mem : x ∈ Set.singleton 0
i : ℕ
mem' : x = 0
⊢ Even x