lean_workbook_plus_70394

Proved

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

Let $P(x,y)$ be the assertion $f(x+y)f(f(x)-y)=xf(x)-yf(y)$

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_70394 (f : ℤ → ℤ) (hf: f = fun x ↦ x) : ∀ x y, f (x + y) * f (f x - y) = x * f x - y * f y   :=  by sorry

Source