lean_workbook_plus_71668

Proved

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

Given the functional equation $f(f(x))=f(x)+8x$ , show that $f$ is injective.

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_71668 (f : ℝ → ℝ) (hf : ∀ x, f (f x) = f x + 8 * x) : Function.Injective f   :=  by sorry

Source