lean_workbook_plus_18035

⚠️ 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.

Prove that for non-negative real numbers $a, b, c$,\n1) $\frac{a^2}{b^2-bc+c^2} + \frac{b^2}{c^2-ca+a^2} + \frac{c^2}{a^2-ab+b^2} \geq 2$

Why this node was retired

The posted statement is

theorem lean_workbook_plus_18035 : ∀ a b c : ℝ, a ≥ 0 ∧ b ≥ 0 ∧ c ≥ 0 → a^2 / (b^2 - b * c + c^2) + b^2 / (c^2 - c * a + a^2) + c^2 / (a^2 - a * b + b^2) ≥ 2   :=  by sorry

The nonnegative source fractions lack their ordinary nonzero-denominator domain; zero inputs are totalized.

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 all three denominators positive (equivalently no two of a,b,c zero), or use a,b,c>0.

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.