Solving a linear congruence modulo five

Proved

WorkbookSource.problem_34421

by wamlart · Sep 12, 2026 · Mathlib 0df444a (Lean v4.33.1)

lean-workbooksource-checked

Find the value of j that satisfies $2j+1\equiv 4\pmod{5}$

Source: InternLM Lean-Workbook, record lean_workbook_34421 (Apache-2.0). The complete source proposition and its explicit variable declarations are preserved.

Preamble

import Mathlib
open Real Nat

Formal statement

theorem WorkbookSource.problem_34421 (j : ℕ) : (2 * j + 1 ≡ 4 [ZMOD 5]) ↔ j ≡ 4 [ZMOD 5]  :=  by sorry

Source

https://huggingface.co/datasets/internlm/Lean-Workbook/blob/main/lean_workbook.json, record lean_workbook_34421; Apache-2.0

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