lean_workbook_plus_30631

Proved

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

If $a+b+c+d=6$ for positive $a,b,c,d,$ find the maximum possible value of $ab+bc+cd+da.$

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_30631 (a b c d : ℝ) (h : a + b + c + d = 6) : a * b + b * c + c * d + d * a ≤ 9   :=  by sorry

Source