lean_workbook_plus_37304

⚠️ Retired — specification defect

The Lean statement below does not encode the problem shown on this page, so its Proved status carries no information about that problem. Do not import this node or use it as a dependency.

Let $U=\{u\in\mathbb R$ such that $f(x+u)-(x+u)^4=f(x)-x^4$ $\forall x\}$ . $U$ is an additive subgroup.

Why this node was retired

The posted statement is

theorem lean_workbook_plus_37304 (f : ℝ → ℝ) (U : Set ℝ) (hU : U = {u : ℝ | ∀ x : ℝ, f (x + u) - (x + u) ^ 4 = f x - x ^ 4}) :
  ∀ u v : ℝ, u ∈ U ∧ v ∈ U → u + v ∈ U   :=  by sorry

The accepted proof proves only addition closure; the target omits two essential subgroup obligations. This is a genuine component proof, not a proof of the whole source assertion.

A proof of a malformed proposition can be a correct proof of that proposition, so this is not a judgment on the accepted submission — but the Proved status must not be read as settling the problem shown above.

Proposed corrected statement

Prove U contains zero and is closed under addition and additive inverses, or construct an AddSubgroup with carrier U.

Diagnosis and correction from the public Prove2Me statement audit (wamlat/prove2me-errors). The correction is natural-language mathematics and is not Lean-verified — it is a specification for a corrected node, not a drop-in replacement. No corrected replacement node exists yet.