α : Type u_1
inst✝² : CancelCommMonoidWithZero α
inst✝¹ : NormalizedGCDMonoid α
inst✝ : DecidableEq α
s₁ s₂ : Multiset α
⊢ ∀ (a : α), a ∈ ndunion s₁ s₂ ↔ a ∈ s₁ + s₂
α : Type u_1
inst✝² : CancelCommMonoidWithZero α
inst✝¹ : NormalizedGCDMonoid α
inst✝ : DecidableEq α
s₁ s₂ : Multiset α
⊢ lcm (ndunion s₁ s₂) = GCDMonoid.lcm (lcm s₁) (lcm s₂)
rw [← lcm_dedup, dedup_ext.2, lcm_dedup, lcm_add]
no goals
α : Type u_1
inst✝² : CancelCommMonoidWithZero α
inst✝¹ : NormalizedGCDMonoid α
inst✝ : DecidableEq α
s₁ s₂ : Multiset α
⊢ ∀ (a : α), a ∈ ndunion s₁ s₂ ↔ a ∈ s₁ + s₂
simp