∀ {R₁ : Type u_3} [inst : CommRing R₁] {K : Type u_4} [inst_1 : Field K] [inst_2 : Algebra R₁ K]
  [inst_3 : IsFractionRing R₁ K] [inst_4 : IsDomain R₁] {I : FractionalIdeal (nonZeroDivisors R₁) K}, I * (1 / I) ≤ 1