simp only [Nat.cast_succ]
case neg.a.inr.e_a.e_a
R : Type u_1
inst✝ : CommRing R
p : R[X]
r : R
hp : ¬p.natDegree = 0
i : ℕ
h : i ≤ (derivative p).natDegree
h' : (derivative p).natDegree < p.natDegree
⊢ ↑p.natDegree - ↑i.succ = ↑(derivative p).natDegree - ↑i + (↑p.natDegree - ↑(derivative p).natDegree.succ)
case neg.a.inr.e_a.e_a
R : Type u_1
inst✝ : CommRing R
p : R[X]
r : R
hp : ¬p.natDegree = 0
i : ℕ
h : i ≤ (derivative p).natDegree
h' : (derivative p).natDegree < p.natDegree
⊢ ↑p.natDegree - (↑i + 1) = ↑(derivative p).natDegree - ↑i + (↑p.natDegree - (↑(derivative p).natDegree + 1))