Theorem: Tutorial.mul_inv_rev (Solution/Advanced/Algebra/Lecture1.lean)

State before:
A : Type ?u.19458
G : Type
inst✝¹ : Ring A
inst✝ : Group G
a b : G
⊢ (a * b)⁻¹ = b⁻¹ * a⁻¹
Tactic:
apply inv_eq_of_mul_eq_one_left
State after:
case a
A : Type ?u.19458
G : Type
inst✝¹ : Ring A
inst✝ : Group G
a b : G
⊢ b⁻¹ * a⁻¹ * (a * b) = 1

State before:
case a
A : Type ?u.19458
G : Type
inst✝¹ : Ring A
inst✝ : Group G
a b : G
⊢ b⁻¹ * a⁻¹ * (a * b) = 1
Tactic:
rw [← mul_assoc]
State after:
case a
A : Type ?u.19458
G : Type
inst✝¹ : Ring A
inst✝ : Group G
a b : G
⊢ b⁻¹ * a⁻¹ * a * b = 1

State before:
case a
A : Type ?u.19458
G : Type
inst✝¹ : Ring A
inst✝ : Group G
a b : G
⊢ b⁻¹ * a⁻¹ * a * b = 1
Tactic:
simp
State after:
no goals