lean_workbook_plus_23358

⚠️ Retired — specification defect

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

Let $P(x,y)$ be the assertion $f(2f(x)+y)=x+f(2f(y)-x)$

Why this node was retired

The posted statement is

theorem lean_workbook_plus_23358 (f : ℤ → ℤ) (hf: f = fun x ↦ x) : ∀ x y, f (2 * f x + y) = x + f (2 * f y - x)   :=  by sorry

The excerpt only introduces P(x,y); the full question and intended solution family are absent.

The recorded counterexample refutes the statement as encoded. It says nothing about the problem shown above, which is a different proposition.

Proposed corrected statement

Restore the functional equation as a condition in the original function-classification problem; remove the invented premise f=id and its false claimed consequence.

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.