simp_rw [degRes_ones]
α : Type u_1
G : SimpleGraph α
inst✝² : Fintype α
inst✝¹ : DecidableEq α
inst✝ : DecidableRel G.Adj
B A : Finset α
⊢ ∑ v in B, degRes G v A = ∑ v in B, ∑ w in A, if Adj G v w then 1 else 0
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