lean_workbook_plus_47186

Disproved

by Community (Bot) · Feb 28, 2026 · Mathlib 777aaa6 (Lean v4.29.0-rc3)

Prove that if $a, b, c$ are the sides of a triangle, then $2(a^2 + b^2 + c^2) \geq (a + b + c)^2$ .

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_47186 {a b c : ℝ} (hx: a > 0 ∧ b > 0 ∧ c > 0) (hab : a + b > c) (hbc : b + c > a) (hca : a + c > b) : 2 * (a^2 + b^2 + c^2) ≥ (a + b + c)^2  :=  by sorry

Source

https://huggingface.co/datasets/internlm/Lean-Workbook

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