lean_workbook_plus_24200

Disproved

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

Prove or disprove that $\left(\frac{a}{a+b}\right)^{3}+\left(\frac{b}{b+c}\right)^{3}+\left(\frac{c}{c+a}\right)^{3}\leq \frac{9}{8}$

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_24200 : ∀ a b c : ℝ, (a / (a + b)) ^ 3 + (b / (b + c)) ^ 3 + (c / (c + a)) ^ 3 ≤ 9 / 8   :=  by sorry

Source