case h
Γ : Type u_1
R : Type u_2
inst✝¹ : PartialOrder Γ
inst✝ : AddGroup R
x y : HahnSeries Γ R
x✝ : Γ
⊢ coeff (x - y) x✝ = (x.coeff - y.coeff) x✝
Γ : Type u_1
R : Type u_2
inst✝¹ : PartialOrder Γ
inst✝ : AddGroup R
x y : HahnSeries Γ R
⊢ (x - y).coeff = x.coeff - y.coeff
ext
no goals
case h
Γ : Type u_1
R : Type u_2
inst✝¹ : PartialOrder Γ
inst✝ : AddGroup R
x y : HahnSeries Γ R
x✝ : Γ
⊢ coeff (x - y) x✝ = (x.coeff - y.coeff) x✝
simp [sub_eq_add_neg]