Adding two bivariate quadratics

Proved

WorkbookSource.problem_24885

by wamlart · Sep 12, 2026 · Mathlib 0df444a (Lean v4.33.1)

lean-workbooksource-checked

Add $x^2 - 3xy - y^2$ and $2x^2 + 5xy - 4y^2$ .

Source: InternLM Lean-Workbook, record lean_workbook_24885 (Apache-2.0). The complete source proposition and explicit variable declarations are preserved.

Preamble

import Mathlib
open Real Nat

Formal statement

theorem WorkbookSource.problem_24885 (x y : ℝ) : x^2 - 3*x*y - y^2 + (2*x^2 + 5*x*y - 4*y^2) = 3*x^2 + 2*x*y - 5*y^2  :=  by sorry

Source

https://huggingface.co/datasets/internlm/Lean-Workbook/blob/main/lean_workbook.json, record lean_workbook_24885; Apache-2.0

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