lean_workbook_plus_55815

⚠️ 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.

Find the exact values of all ordered pairs of numbers $(x,y)$ which satisfy the following system of equations: \n$x^2 - xy + y^2 = 7$ \n$x - xy + y = -1$

Why this node was retired

The posted statement is

theorem lean_workbook_plus_55815 (x y : ℝ) (h₁ : x^2 - x*y + y^2 = 7) (h₂ : x - x*y + y = -1) : x = 2 ∧ y = 1 ∨ x = -2 ∧ y = -1   :=  by sorry

The inserted two-point solution set is wrong.

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

Proposed corrected statement

Prove the system x²−xy+y²=7, x−xy+y=−1 has exactly (2,3),(3,2),(−1+√2,−1−√2),(−1−√2,−1+√2).

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.