lean_workbook_plus_22780

⚠️ 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 $a,b >0$ and $a^3+2b^3=2.$ Prove that

Why this node was retired

The posted statement is

theorem lean_workbook_plus_22780 (a b : ℝ) (ha : 0 < a) (hb : 0 < b) (hab : a^3 + 2 * b^3 = 2) : a + 2 * b + (1 / 5) * (a^2 - b^2)^2 ≤ (18:ℝ)^(1 / 3)   :=  by sorry

Interpret the cube root as a real odd cube root, not a natural power with exponent1/3.

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

Confirmed directly from the Lean text: the numeric-literal exponent carries no type ascription, so it elaborates at type ℕ where division truncates (^(1 / 3) → ^0).

Proposed corrected statement

Interpret the cube root as a real odd cube root, not a natural power with exponent1/3.

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.