lean_workbook_plus_15093

Proved

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

Prove that $(x+y+z-3)(2(x+y+z)-3)\ge 0$ given $x+y+z \geq 3$ .

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_15093 (x y z : ℝ) (h : x + y + z ≥ 3) :
  (x + y + z - 3) * (2 * (x + y + z) - 3) ≥ 0   :=  by sorry

Source