apply and_congr_right'
α : Type u
inst✝ : DecidableEq α
as : Array α
a : α
⊢ (Nodup as ∧ ∀ (a_1 : α), a_1 ∈ as → a_1 ≠ a) ↔ Nodup as ∧ ¬a ∈ as
case h
α : Type u
inst✝ : DecidableEq α
as : Array α
a : α
⊢ (∀ (a_1 : α), a_1 ∈ as → a_1 ≠ a) ↔ ¬a ∈ as