lean_workbook_plus_28717

Proved

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

Prove that $a^2+b^2+c^2 \geq 2(a+b+c)-3$

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_28717 (a b c : ℝ) : a^2+b^2+c^2 ≥ 2*(a+b+c)-3   :=  by sorry

Source