Theorem: Section7sheet1.conjugate.inv_mem (FormalisingMathematics2024/Section07subgroupsAndHomomorphisms/Sheet1.lean)

State before:
G : Type
inst✝ : Group G
a b : G
H K : Subgroup G
x y z : G
hy : y ∈ {a | ∃ h ∈ H, a = x * h * x⁻¹}
⊢ y⁻¹ ∈ {a | ∃ h ∈ H, a = x * h * x⁻¹}
Tactic:
sorry
State after:
no goals