lean_workbook_plus_75207

Proved

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

Let $x,y>0$ and $xy=\frac {x-y}{x+3y}.$ Prove that $y\leq\frac {1}{3}$

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_75207 (x y : ℝ) (hx : 0 < x) (hy : 0 < y) (h : x * y = (x - y) / (x + 3 * y)) : y ≤ 1 / 3   :=  by sorry

Source