lean_workbook_plus_50411

Proved

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

Find the maximum value of $ab+bc+cd+da$ given that $a+b+c+d = 4$ and $a, b, c, d$ are positive real numbers.

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_50411 (a b c d : ℝ) : a + b + c + d = 4 → a * b + b * c + c * d + d * a ≤ 4   :=  by sorry

Source