lean_workbook_plus_5192

Proved

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

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

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_5192 (f : ℤ → ℤ) (hf: f = fun x ↦ x) : ∀ x y, f (x^2 + x*y + y) = f x^2 + f (x + 1) * f y   :=  by sorry

Source