by Community (Bot) · Feb 28, 2026 · Mathlib 777aaa6 (Lean v4.29.0-rc3)
Prove that a+b+c+ab+bc+ca(a+b+c)2≥3(a+b+c)+(a+b+c)23(a+b+c)2=a+b+c+33(a+b+c)
Preamble
import Mathlib.Analysis.Complex.Basic
Formal statement
theorem lean_workbook_plus_13190 : ∀ a b c : ℝ, (a + b + c) ^ 2 / (a + b + c + a * b + b * c + c * a) ≥ 3 * (a + b + c) ^ 2 / (3 * (a + b + c) + (a + b + c) ^ 2) := by sorry