English
In ArchimedeanClass over an ordered ring, if x ≠ ⊤ and x+y = x+z then y=z.
Русский
В ArchimedeanClass над упорядоченным кольцом, если x ≠ ⊤ и x+y = x+z, то y=z.
LaTeX
$$$\forall x,y,z \in \operatorname{ArchimedeanClass}(R),\ x \neq \top \rightarrow x+y = x+z \rightarrow y=z.$$$
Lean4
theorem nonneg [Semiring R] [LinearOrder R] [ExistsAddOfLE R] [PosMulMono R] [AddLeftMono R] {x : R} (h : IsSquare x) :
0 ≤ x := by
rcases h with ⟨y, rfl⟩
exact mul_self_nonneg y