simp only [mul_inv_cancel hc4, one_mul]
case neg.refine_3
K : Type u
inst✝¹ : Field K
inst✝ : ECTate.PerfectRing K
e : Model K
h : discr e = 0
hc4 : ¬c4 e = 0
⊢ c4 e * (c4 e)⁻¹ * (2 * (b2 e * b5 e + 3 * b7 e) + e.a1 * (18 * b6 e - b2 e * b4 e)) + c4 e * e.a3 = 0
case neg.refine_3
K : Type u
inst✝¹ : Field K
inst✝ : ECTate.PerfectRing K
e : Model K
h : discr e = 0
hc4 : ¬c4 e = 0
⊢ 2 * (b2 e * b5 e + 3 * b7 e) + e.a1 * (18 * b6 e - b2 e * b4 e) + c4 e * e.a3 = 0