BT004E · Bertrand theorem

mod_eq_predecessor_cancel

Stable checked-use theorem · independently kernel verified

The predecessor of a successor acts as minus one in balanced congruence.

Current library: Alpha v34, 4,223 checked-use theorems; Stable remains 432. Historical first admissions, original proof editions, and non-admitted aliases are preserved. Exact original first-admission records.

Statement with defined notation

∀ k. ∀ a. ∀ z. ModEq(S k,a + z + k · z,a)

Every purple notation token opens its conservative definition. Expanding the displayed statement recovers the exact first-order Peano-arithmetic formula checked by the unchanged kernel.

Definitions used by this theorem

In the theorem statement

1 occurrences

In local proof propositions

none

0 occurrences

Exact expanded native-PA statement
forall k a z. exists u v. ((a + z) + k * z) + S k * u = a + S k * v

Proof neighborhood

Direct theorem prerequisites

Direct theorem dependents

Definition-aware tactic body

Only local propositions introduced by have or suffices are compacted. Every changed line has an exact-AST conservative-expansion receipt; the kernel still receives the immutable original tactic script.

Read the argument

Proof checkpoints

15 script commands · 8 reading checkpoints · 0 local claims

This is a reading aid, not a new proof or a proof-tree certificate. Checkpoint groups are consecutive commands, not inferred branch boundaries. Every step links to the preserved script.

Definition notation is shown below. Open the paired exact edition for the original native formulas. Source pairing is not a new equivalence certificate.

Named ingredients (3)
01Fix variables and assumptionsL1–3

Work with arbitrary variables or the premises of the current implication.

  1. L1
    intro k
  2. L2
    intro a
  3. L3
    intro z
02Construct an explicit witnessL4–5

Supply the displayed value, then prove that it has the required property.

  1. L4
    exists 0
  2. L5
    exists z
03Calculate and transport equalitiesL6–7

Carry out the recorded arithmetic or equality steps; inspect the exact commands for their direction and premises.

  1. L6
    rewrite PA5
  2. L7
    rewrite PA3
04Use earlier factsL8–9

Instantiate or apply named facts and discharge the corresponding proof obligations.

  1. L8
    specialize mul_succ_left k
  2. L9
    specialize mul_succ_left z
05Calculate and transport equalitiesL10–11

Carry out the recorded arithmetic or equality steps; inspect the exact commands for their direction and premises.

  1. L10
    rewrite mul_succ_left
  2. L11
    trans a + (z + k * z)
06Use earlier factsL12–12

Instantiate or apply named facts and discharge the corresponding proof obligations.

  1. L12
    apply add_assoc
07Calculate and transport equalitiesL13–14

Carry out the recorded arithmetic or equality steps; inspect the exact commands for their direction and premises.

  1. L13
    congr
  2. L14
    refl
08Use earlier factsL15–15

Instantiate or apply named facts and discharge the corresponding proof obligations.

  1. L15
    apply add_comm

Library-wide reading audit

Original defined command ledger · 15 lines
  1. 0001intro k
  2. 0002intro a
  3. 0003intro z
  4. 0004exists 0
  5. 0005exists z
  6. 0006rewrite PA5
  7. 0007rewrite PA3
  8. 0008specialize mul_succ_left k
  9. 0009specialize mul_succ_left z
  10. 0010rewrite mul_succ_left
  11. 0011trans a + (z + k * z)
  12. 0012apply add_assoc
  13. 0013congr
  14. 0014refl
  15. 0015apply add_comm