lean_workbook_plus_4574

Proved

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

If $x$ is odd, prove that $x^2+1$ is even but not divisible by 4.

Preamble

import Mathlib.Analysis.Complex.Basic

Formal statement

theorem lean_workbook_plus_4574 (x : ℤ) (h : x % 2 = 1) : (x ^ 2 + 1) % 2 = 0 ∧ (x ^ 2 + 1) % 4 ≠ 0   :=  by sorry

Source