lean_workbook_plus_12743

Proved

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

$2(a + b + c)^2\leq{3(a^2 + b^2 + c^2 + ab + bc + ca)}$

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_12743 : ∀ a b c : ℝ, 2 * (a + b + c) ^ 2 ≤ 3 * (a ^ 2 + b ^ 2 + c ^ 2 + a * b + b * c + c * a)   :=  by sorry

Source