lean_workbook_plus_19894

Proved

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

Prove that for $x+y+z+w=2$ , $(x+z)(y+w)\le 1$ using AM-GM inequality.

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_19894 (x y z w : ℝ) (h : x + y + z + w = 2) :
  (x + z) * (y + w) ≤ 1   :=  by sorry

Source