congr
α : Type u_1
G : SimpleGraph α
inst✝² : Fintype α
inst✝¹ : DecidableEq α
inst✝ : DecidableRel G.Adj
B A : Finset α
⊢ ∑ x in B, ∑ x in nbhdRes G x A, 1 = ∑ v in B, ∑ w in A, if Adj G v w then 1 else 0
case e_f
α : Type u_1
G : SimpleGraph α
inst✝² : Fintype α
inst✝¹ : DecidableEq α
inst✝ : DecidableRel G.Adj
B A : Finset α
⊢ (fun x => ∑ x in nbhdRes G x A, 1) = fun v => ∑ w in A, if Adj G v w then 1 else 0