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Question 17542: Keep the Signed Function Error Separate from Its Absolute Bound

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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R0034-17542 · q-20261014-advance-20261103-r02-pointwise-convergence-of-functions-0017

Original question and givens

Use the same complete finite domain Fin(2)={0,…,1}, with aligned limit values=[16, 17], coefficients=[17, -18], positive shift=2, and f_n(x)=limit[x]+coefficients[x]/(n+shift) for every n≥0. Values and tail bounds are exact rationals. Pointwise witnesses may depend on both x and epsilon. A finite maximum of all pointwise witnesses gives a common witness only on this finite domain; it is not a general infinite-domain implication. A finite observed prefix alone is not a convergence certificate. n=17, point=0. Give (n,point,f_n_x,limit_x,error), where error=f_n(x)−limit[x] is signed.

  • G001 — Use the same complete finite domain Fin(2)={0,…,1}, with aligned limit values=[16, 17], coefficients=[17, -18], positive shift=2, and f_n(x)=limit[x]+coefficients[x]/(n+shift) for every n≥0. Values and tail bounds are exact rationals. Pointwise witnesses may depend on both x and epsilon. A finite maximum of all pointwise witnesses gives a common witness only on this finite domain; it is not a general infinite-domain implication. A finite observed prefix alone is not a convergence certificate. n=17, point=0. Give (n,point,f_n_x,limit_x,error), where error=f_n(x)−limit[x] is signed.

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

same COMPLETE finite domain Fin(2);original aligned limits=[16, 17];signed coefficients=[17, -18];positive shift=2

After

declared for EVERY n>=0:f_n(x)=limit[x]+coefficient[x]/(n+shift);signed error=f_n(x)-limit[x]=coefficient[x]/(n+shift)

Conditions: none

The complete common finite domain and all-n formula are declared premises,not extrapolated from samples.Function values and errors are not probabilities;they may be signed or exceed1.Do not clip or shift indices.

Step identifiers and dependencies

Rule: pointwise_explicit_common_domain_all_n_tail_not_probability · Uses: G001

S002 · calculation

Before

selected function evaluation denominator := sum(17, 2)

After

selected function evaluation denominator = 19

Conditions: none

Compute exactly from original roles and established intermediates,retaining denominators,signs,indices and strict conditions.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S001

S003 · calculation

Before

selected function evaluation signed correction := div(17, 19)

After

selected function evaluation signed correction = 17/19

Conditions: none

Compute exactly from original roles and established intermediates,retaining denominators,signs,indices and strict conditions.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S002

S004 · calculation

Before

selected function evaluation function value := sum(16, 17/19)

After

selected function evaluation function value = 321/19

Conditions: none

Compute exactly from original roles and established intermediates,retaining denominators,signs,indices and strict conditions.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S003

S005 · calculation

Before

selected function evaluation reverse signed error := sub(321/19, 16)

After

selected function evaluation reverse signed error = 17/19

Conditions: none

Compute exactly from original roles and established intermediates,retaining denominators,signs,indices and strict conditions.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S004

S006 · implies

Before

selected function evaluation:original point=0;n=17;limit=16;signed coefficient=17

After

f_n(x)=321/19;f_n(x)-limit=17/19;this error field remains SIGNED

Conditions: none

Add the correction to the limit,then subtract the limit to reverse-check the error.Keep the evaluate field signed;only the epsilon bound uses absolute value.

Step identifiers and dependencies

Rule: pointwise_selected_value_reverse_error_not_absolute_value · Uses: G001, S005

Reverse checks

  • 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 selected function evaluation reverse signed error with exact rational arithmetic, not rounded decimals.
  • S004 · premise_and_result_audit — Recompute selected function evaluation function value with exact rational arithmetic, not rounded decimals.
  • S003 · premise_and_result_audit — Recompute selected function evaluation signed correction with exact rational arithmetic, not rounded decimals.
  • S002 · premise_and_result_audit — Recompute selected function evaluation denominator with exact rational arithmetic, not rounded decimals.
  • S001 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.

Result

(17, 0, 321/19, 16, 17/19)

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: b857bc5a7c28ea576fc44d3c83a7977a2042793095b28d485ff9f650b81d2f93
  • candidate record SHA-256: d119922610ad165fccdb74f3e22af0574c1407108ab236d46b1a70bbb3e8ae75
  • semantic review receipt SHA-256: f73d099ebe3ff1c69a5d96f08c75b11b9e5b05120af40cf3ef388fce3b5c5336
  • question-first witness SHA-256: 22675ffb6209b4fea076032b29b96e3dc19aad4244c54493f5f65f5e5d875699
  • Lean: NOT_RUN · human review: NOT_PERFORMED
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