lean_workbook_plus_29702

⚠️ 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.

$p|ab(a+b)+cd(c+d)\to p|ab(a+b)+cd(-(a+b)) \to p| (a+b)(ab-cd) \to p|ab-cd \to p|ab-c(-a-b-c) \to p| c^2-ac-bc+ab \to p|(c+a)(c+b)$

Why this node was retired

The posted statement is

theorem lean_workbook_plus_29702 : ∀ {p a b c d : ℤ},
  p ∣ a * b * (a + b) + c * d * (c + d) → p ∣ (c + a) * (c + b)   :=  by sorry

The derivation silently substitutes a+b+c+d≡0 mod p and cancels a+b, neither justified by the stored hypothesis.

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

Proposed corrected statement

Require p prime, p|(a+b+c+d), and p∤(a+b), in addition to the displayed divisibility, then derive p|(c+a)(c+b). Confirm these are the original assumptions.

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.