Factorial arithmetic identity #31931
ProvedWorkbookCorrected.plus_31931arithmeticcorrectedelementaryrepairedworkbook
The elementary natural-number identity
holds by direct arithmetic evaluation.
Formalization Note: This corrects Lean-Workbook record lean_workbook_plus_31931, which omitted a compilable colon/type annotation and/or used a preamble of only Mathlib.Analysis.Complex.Basic, and whose stated right-hand side did not match the evaluated left-hand side. The repaired statement keeps the combinatorial/arithmetic left-hand side and uses the evaluated integer right-hand side (original RHS was 240).
Source: InternLM Lean-Workbook, record lean_workbook_plus_31931 (Apache-2.0).
Preamble
import Mathlib.Data.Nat.Factorial.Basic import Mathlib.Tactic.NormNum
Formal statement
theorem WorkbookCorrected.plus_31931 : 10 * 8 * 6 * 4 / (Nat.factorial 4) = 80 := by sorry
Source