lean_workbook_plus_75821

Proved

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

Let $P(x,y)$ be the assertion $f(xf(y)-1)+f(xy)=2xy-1$

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_75821 (f : ℤ → ℤ) (hf: f = fun x ↦ x) : ∀ x y, f (x * f y - 1) + f (x * y) = 2 * x * y - 1   :=  by sorry

Source