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Question 10570: A Conditional Uniqueness Check Is Not Two Convergence Claims

On this page
  1. Original question and givens
  2. Definition and scope
  3. Step-by-step derivation
  4. Reverse checks
  5. Result
  6. This question review and source binding

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R0020-10570 · q-20261013-advance-20261023-r04-metric-convergence-0095

Original question and givens

Use the complete qualified finite metric table=[[0, 20, 41, 63], [20, 0, 21, 43], [41, 21, 0, 22], [63, 43, 22, 0]] on Fin(4)={0,…,3}. Preserve the convergence quantifiers: for every positive epsilon there exists N such that every n≥N satisfies d(x_n,candidate)<epsilon. A finite recorded tail alone does not certify this infinite statement. infinite sequence has prefix=[3, 0] and constant tail=1; candidates a=1, b=2. Give (prefix,tail,a,b,d(a,b),a is a limit?,b is a limit?,if both are limits then a=b?).

  • G001 — Use the complete qualified finite metric table=[[0, 20, 41, 63], [20, 0, 21, 43], [41, 21, 0, 22], [63, 43, 22, 0]] on Fin(4)={0,…,3}. Preserve the convergence quantifiers: for every positive epsilon there exists N such that every n≥N satisfies d(x_n,candidate)<epsilon. A finite recorded tail alone does not certify this infinite statement. infinite sequence has prefix=[3, 0] and constant tail=1; candidates a=1, b=2. Give (prefix,tail,a,b,d(a,b),a is a limit?,b is a limit?,if both are limits then a=b?).

Definition and scope

Use the original question domain, assumptions and cited MKO definitions. This item has second-context mathematical and bilingual review, with the model, answer and every arithmetic step independently recomputed from the original parameters; the source question remains a candidate.

Step-by-step derivation

S001 · implies

Before

carrier Fin(4);complete distance table=[[0, 20, 41, 63], [20, 0, 21, 43], [41, 21, 0, 22], [63, 43, 22, 0]]

After

nonnegative typed entries=Yes;zero iff equal=Yes;symmetric=Yes;all triangle tests=Yes

Conditions: none

Qualify the whole metric table,not only queried cells.Labels are not distances:diagonal zero,positive separation,symmetry and every triangle condition are premises for later reasoning.

Step identifiers and dependencies

Rule: whole_qualified_finite_metric · Uses: G001

S002 · implies

Before

phase=candidate a;prefix=[3, 0];all later terms explicitly equal=1

After

candidate=1;infinite constant tail begins at=2

Conditions: none

The problem explicitly specifies every later term as tail;this is not guessing an infinite rule from a finite prefix.The prefix does not change the tail limit.

Step identifiers and dependencies

Rule: declared_infinite_tail_not_pattern_guess · Uses: G001, S001

S003 · implies

Before

phase=candidate a;candidate=tail=1;distance=0

After

for every epsilon>0 choose N=2;every n>=N has distance0<epsilon

Conditions: none

Retain the order for every epsilon>0 there exists N such that every n≥N works.N equal to prefix length works for every positive epsilon.

Step identifiers and dependencies

Rule: constant_tail_full_quantified_witness · Uses: G001, S002

S004 · implies

Before

phase=candidate b;prefix=[3, 0];all later terms explicitly equal=1

After

candidate=2;infinite constant tail begins at=2

Conditions: none

The problem explicitly specifies every later term as tail;this is not guessing an infinite rule from a finite prefix.The prefix does not change the tail limit.

Step identifiers and dependencies

Rule: declared_infinite_tail_not_pattern_guess · Uses: G001, S003

S005 · calculation

Before

candidate b separating epsilon := div(21, 2)

After

candidate b separating epsilon = 21/2

Conditions: none

Compute exactly with this step's original roles and operands,without floating approximation or reordering source data.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S004

S006 · implies

Before

phase=candidate b;tail distance=21;epsilon=21/2

After

for any proposed N choose n=max(N,2);distance=21>=epsilon

Conditions: none

Metric separation gives positive distance.Choose half of it as epsilon;after every proposed N a tail term retains that distance and violates the full-tail convergence condition.

Step identifiers and dependencies

Rule: constant_tail_nonlimit_counterwitness · Uses: G001, S005

S007 · implies

Before

a limit=Yes;b limit=No;distance(a,b)=21

After

if both are limits then a=b=Yes

Conditions: none

Audit both limit qualifications separately.The last field is conditional implication;it can be true with a false antecedent and does not assert both candidates converge.

Step identifiers and dependencies

Rule: limit_uniqueness_conditional_not_two_claims · Uses: G001, S006

Reverse checks

  • S007 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S006 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S005 · premise_and_result_audit — Recompute candidate b separating epsilon with exact rational arithmetic, not rounded decimals.
  • S004 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S003 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S002 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S001 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.

Result

([3, 0], 1, 1, 2, 21, Yes, No, Yes)

The full substitutions and premise checks give the original answer; source identity,format and status are unchanged.

This question review and source binding

Review date: 2026-10-26

Original questions, answers, step expressions, numeric ASTs and historical records are retained. Source candidate labels remain historical and are not overwritten as formal proof.

Source hashes and review receipts
  • input commit: 0f7be61e2c22317a4075561dc822c87d881a50db
  • original question SHA-256: 2fc85fea837498029d076cb7f306dc8175323f7a681ad0bf5d29dcfc3725b5e2
  • candidate record SHA-256: 86840711203ebffce5fe708e9c1b79e85e0c6041f58fc5e75a2866f5afd71d8b
  • semantic review receipt SHA-256: b4c47938fd38085d44967226cfa8337d61334455472e7307c60d3a488cef598f
  • question-first witness SHA-256: 3c23baa97a5933bc07b44f2257017ef4e845bf1429bd6f5381410681c43b97e4
  • Lean: NOT_RUN · human review: NOT_PERFORMED
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