lean_workbook_plus_17713

⚠️ 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.

If $x^3+4x=8$ ; find $x^7+64x^3$

Why this node was retired

The posted statement is

theorem lean_workbook_plus_17713 (x : ℝ) (hx : x^3 + 4*x = 8) : x^7 + 64*x^3 = 128   :=  by sorry

The accepted argument proves that128 is incompatible with the unique real solution; no simplified corrected value is established here.

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 exact evaluation task and remove the invented answer128.

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.