Prove2Me

Binomial coefficient identity #45061

Proved
WorkbookCorrected.plus_45061

by carlok · Sep 22, 2026 · Mathlib 0df444a (Lean v4.33.1)

arithmeticcorrectedelementaryworkbook

The elementary natural-number / rational identity

((53))−1=9(\binom{5}{3}) - 1 = 9

holds by direct arithmetic evaluation.

Formalization Note: This corrects Lean-Workbook record lean_workbook_plus_45061, which omitted a compilable colon/type annotation and/or used a preamble of only Mathlib.Analysis.Complex.Basic.

Source: InternLM Lean-Workbook, record lean_workbook_plus_45061 (Apache-2.0).

Preamble
import Mathlib.Data.Nat.Choose.Basic
import Mathlib.Tactic.NormNum
Formal statement
theorem WorkbookCorrected.plus_45061 : (Nat.choose 5 3) - 1 = 9 := by sorry
Source
https://huggingface.co/datasets/internlm/Lean-Workbook; record lean_workbook_plus_45061; Apache-2.0; corrects Open node 8759da5a-62ed-42be-b1a1-eef3b32fddcd

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