-- Mathlib/RingTheory/Binomial.lean
theorem ascPochhammer_succ_succ (r : R) (k : ℕ) :
    smeval (ascPochhammer ℕ (k + 1)) (r + 1) = Nat.factorial (k + 1) • multichoose (r + 1) k +
    smeval (ascPochhammer ℕ (k + 1)) r

Proof state:
R : Type u_2
inst✝³ : NonAssocSemiring R
inst✝² : Pow R ℕ
inst✝¹ : NatPowAssoc R
inst✝ : BinomialRing R
r : R
k : ℕ
⊢ ((r + 1) ^ 1 + (↑k).smeval (r + 1)) * (ascPochhammer ℕ k).smeval (r + 1) =
    (k + 1).factorial • multichoose (r + 1) k + r ^ 1 * (ascPochhammer ℕ k).smeval (r ^ 1 + smeval 1 r)

Tactic:
rw [Nat.factorial, mul_smul, factorial_nsmul_multichoose_eq_ascPochhammer]

Result:
R : Type u_2
inst✝³ : NonAssocSemiring R
inst✝² : Pow R ℕ
inst✝¹ : NatPowAssoc R
inst✝ : BinomialRing R
r : R
k : ℕ
⊢ ((r + 1) ^ 1 + (↑k).smeval (r + 1)) * (ascPochhammer ℕ k).smeval (r + 1) =
    k.succ • (ascPochhammer ℕ k).smeval (r + 1) + r ^ 1 * (ascPochhammer ℕ k).smeval (r ^ 1 + smeval 1 r)

Proof state:
R : Type u_2
inst✝³ : NonAssocSemiring R
inst✝² : Pow R ℕ
inst✝¹ : NatPowAssoc R
inst✝ : BinomialRing R
r : R
k : ℕ
⊢ r * (ascPochhammer ℕ k).smeval (r + 1) +
      (↑↑k * (ascPochhammer ℕ k).smeval (r + 1) + 1 * (ascPochhammer ℕ k).smeval (r + 1)) =
    k.succ • (ascPochhammer ℕ k).smeval (r + 1) + r * (ascPochhammer ℕ k).smeval (r + 1)

Tactic:
rw [← @nsmul_eq_mul, @add_rotate', @succ_nsmul, add_assoc]

Result:
R : Type u_2
inst✝³ : NonAssocSemiring R
inst✝² : Pow R ℕ
inst✝¹ : NatPowAssoc R
inst✝ : BinomialRing R
r : R
k : ℕ
⊢ ↑k • (ascPochhammer ℕ k).smeval (r + 1) +
      (1 * (ascPochhammer ℕ k).smeval (r + 1) + r * (ascPochhammer ℕ k).smeval (r + 1)) =
    k • (ascPochhammer ℕ k).smeval (r + 1) +
      ((ascPochhammer ℕ k).smeval (r + 1) + r * (ascPochhammer ℕ k).smeval (r + 1))

Proof state:
R : Type u_2
inst✝³ : NonAssocSemiring R
inst✝² : Pow R ℕ
inst✝¹ : NatPowAssoc R
inst✝ : BinomialRing R
r : R
k : ℕ
⊢ (ascPochhammer ℕ (k + 1)).smeval (r + 1) =
    (k + 1).factorial • multichoose (r + 1) k + (ascPochhammer ℕ (k + 1)).smeval r

Tactic:
nth_rw 1 [ascPochhammer_succ_right, ascPochhammer_succ_left, mul_comm (ascPochhammer ℕ k)]

Result:
R : Type u_2
inst✝³ : NonAssocSemiring R
inst✝² : Pow R ℕ
inst✝¹ : NatPowAssoc R
inst✝ : BinomialRing R
r : R
k : ℕ
⊢ ((X + ↑k) * ascPochhammer ℕ k).smeval (r + 1) =
    (k + 1).factorial • multichoose (r + 1) k + (X * (ascPochhammer ℕ k).comp (X + 1)).smeval r

Proof state:
R : Type u_2
inst✝³ : NonAssocSemiring R
inst✝² : Pow R ℕ
inst✝¹ : NatPowAssoc R
inst✝ : BinomialRing R
r : R
k : ℕ
⊢ (r + 1 + (↑k).smeval (r + 1)) * (ascPochhammer ℕ k).smeval (r + 1) =
    k.succ • (ascPochhammer ℕ k).smeval (r + 1) + r * (ascPochhammer ℕ k).smeval (r + 1)

Tactic:
rw [← C_eq_natCast, smeval_C, npow_zero, add_assoc, add_mul, add_comm 1, @nsmul_one, add_mul]

Result:
R : Type u_2
inst✝³ : NonAssocSemiring R
inst✝² : Pow R ℕ
inst✝¹ : NatPowAssoc R
inst✝ : BinomialRing R
r : R
k : ℕ
⊢ r * (ascPochhammer ℕ k).smeval (r + 1) +
      (↑↑k * (ascPochhammer ℕ k).smeval (r + 1) + 1 * (ascPochhammer ℕ k).smeval (r + 1)) =
    k.succ • (ascPochhammer ℕ k).smeval (r + 1) + r * (ascPochhammer ℕ k).smeval (r + 1)

Proof state:
R : Type u_2
inst✝³ : NonAssocSemiring R
inst✝² : Pow R ℕ
inst✝¹ : NatPowAssoc R
inst✝ : BinomialRing R
r : R
k : ℕ
⊢ ↑k • (ascPochhammer ℕ k).smeval (r + 1) +
      (1 * (ascPochhammer ℕ k).smeval (r + 1) + r * (ascPochhammer ℕ k).smeval (r + 1)) =
    k • (ascPochhammer ℕ k).smeval (r + 1) +
      ((ascPochhammer ℕ k).smeval (r + 1) + r * (ascPochhammer ℕ k).smeval (r + 1))

Tactic:
simp_all only [Nat.cast_id, nsmul_eq_mul, one_mul]

Result:
no goals

Proof state:
R : Type u_2
inst✝³ : NonAssocSemiring R
inst✝² : Pow R ℕ
inst✝¹ : NatPowAssoc R
inst✝ : BinomialRing R
r : R
k : ℕ
⊢ ((X + ↑k) * ascPochhammer ℕ k).smeval (r + 1) =
    (k + 1).factorial • multichoose (r + 1) k + (X * (ascPochhammer ℕ k).comp (X + 1)).smeval r

Tactic:
simp only [smeval_mul, smeval_comp, smeval_add, smeval_X]

Result:
R : Type u_2
inst✝³ : NonAssocSemiring R
inst✝² : Pow R ℕ
inst✝¹ : NatPowAssoc R
inst✝ : BinomialRing R
r : R
k : ℕ
⊢ ((r + 1) ^ 1 + (↑k).smeval (r + 1)) * (ascPochhammer ℕ k).smeval (r + 1) =
    (k + 1).factorial • multichoose (r + 1) k + r ^ 1 * (ascPochhammer ℕ k).smeval (r ^ 1 + smeval 1 r)

Proof state:
R : Type u_2
inst✝³ : NonAssocSemiring R
inst✝² : Pow R ℕ
inst✝¹ : NatPowAssoc R
inst✝ : BinomialRing R
r : R
k : ℕ
⊢ ((r + 1) ^ 1 + (↑k).smeval (r + 1)) * (ascPochhammer ℕ k).smeval (r + 1) =
    k.succ • (ascPochhammer ℕ k).smeval (r + 1) + r ^ 1 * (ascPochhammer ℕ k).smeval (r ^ 1 + smeval 1 r)

Tactic:
simp only [smeval_one, npow_one, npow_zero, one_smul]

Result:
R : Type u_2
inst✝³ : NonAssocSemiring R
inst✝² : Pow R ℕ
inst✝¹ : NatPowAssoc R
inst✝ : BinomialRing R
r : R
k : ℕ
⊢ (r + 1 + (↑k).smeval (r + 1)) * (ascPochhammer ℕ k).smeval (r + 1) =
    k.succ • (ascPochhammer ℕ k).smeval (r + 1) + r * (ascPochhammer ℕ k).smeval (r + 1)