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Question 23697: Two Infinite Tails Must Converge Separately before Their Values Are Added

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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← Question derivation index · Original question batch

R0046-23697 · q-20261014-advance-20261112-r04-improper-integral-0072

Original question and givens

Use f(x)=22/abs(x)^3 for x≤−1, f(x)=0 for −1<x<1 and f(x)=23/x^3 for x≥1, with integer exponent≥2. Give (piecewise_integrand, interval, left_tail_integral, right_tail_integral, left_converges, right_converges, sum, certificate).

  • G001 — Use f(x)=22/abs(x)^3 for x≤−1, f(x)=0 for −1<x<1 and f(x)=23/x^3 for x≥1, with integer exponent≥2. Give (piecewise_integrand, interval, left_tail_integral, right_tail_integral, left_converges, right_converges, sum, certificate).

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

source operation=improper-two-sided-independent;original snapshot and mathematics retained

After

explicit ordered source output fields=[piecewise_integrand, interval, left_tail_integral, right_tail_integral, left_converges, right_converges, sum, certificate]

Conditions: none

Keep the source snapshot while listing ordered fields without JavaScript.Radius uses its original mode to select6 or11 fields without padding;distinguish nonclaims from actual negations.

Step identifiers and dependencies

Rule: source_ordered_interface_explicit_without_javascript · Uses: G001

S002 · calculation

Before

Improper ORIGINAL negative tail after x=-u lower positive power step1 := mul(1, 1)

After

Improper ORIGINAL negative tail after x=-u lower positive power step1 = 1

Conditions: none

Substitute original roles and established intermediates exactly,without floats or treating finite tests as universal limits.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S001

S003 · calculation

Before

Improper ORIGINAL negative tail after x=-u lower positive power step2 := mul(1, 1)

After

Improper ORIGINAL negative tail after x=-u lower positive power step2 = 1

Conditions: none

Substitute original roles and established intermediates exactly,without floats or treating finite tests as universal limits.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S002

S004 · calculation

Before

Improper ORIGINAL negative tail after x=-u exponent-minus-one times lower-power := mul(2, 1)

After

Improper ORIGINAL negative tail after x=-u exponent-minus-one times lower-power = 2

Conditions: none

Substitute original roles and established intermediates exactly,without floats or treating finite tests as universal limits.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S003

S005 · calculation

Before

Improper ORIGINAL negative tail after x=-u exact antiderivative limit value := div(22, 2)

After

Improper ORIGINAL negative tail after x=-u exact antiderivative limit value = 11

Conditions: none

Substitute original roles and established intermediates exactly,without floats or treating finite tests as universal limits.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S004

S006 · implies

Before

Improper ORIGINAL negative tail after x=-u:ORIGINAL scale=22,exponent=3>1,lower=1>=1;integrand scale/x^exponent

After

for EVERY B>=lower,integral_lower^B=scale/(exponent-1)*(lower^(1-exponent)-B^(1-exponent));B^(1-exponent) tends0,so limit=11

Conditions: none

Because k>1,the negative power tends0.The absolute tail error is |scale|/((k−1)B^(k−1)),which is below any epsilon for sufficiently large B.Signed or zero scale is allowed;this is a universal limit,not sampled cutoffs.

Step identifiers and dependencies

Rule: improper_WHOLE_one_sided_tail_antiderivative_limit_not_samples · Uses: G001, S005

S007 · calculation

Before

Improper ORIGINAL positive tail lower positive power step1 := mul(1, 1)

After

Improper ORIGINAL positive tail lower positive power step1 = 1

Conditions: none

Substitute original roles and established intermediates exactly,without floats or treating finite tests as universal limits.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S006

S008 · calculation

Before

Improper ORIGINAL positive tail lower positive power step2 := mul(1, 1)

After

Improper ORIGINAL positive tail lower positive power step2 = 1

Conditions: none

Substitute original roles and established intermediates exactly,without floats or treating finite tests as universal limits.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S007

S009 · calculation

Before

Improper ORIGINAL positive tail exponent-minus-one times lower-power := mul(2, 1)

After

Improper ORIGINAL positive tail exponent-minus-one times lower-power = 2

Conditions: none

Substitute original roles and established intermediates exactly,without floats or treating finite tests as universal limits.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S008

S010 · calculation

Before

Improper ORIGINAL positive tail exact antiderivative limit value := div(23, 2)

After

Improper ORIGINAL positive tail exact antiderivative limit value = 23/2

Conditions: none

Substitute original roles and established intermediates exactly,without floats or treating finite tests as universal limits.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S009

S011 · implies

Before

Improper ORIGINAL positive tail:ORIGINAL scale=23,exponent=3>1,lower=1>=1;integrand scale/x^exponent

After

for EVERY B>=lower,integral_lower^B=scale/(exponent-1)*(lower^(1-exponent)-B^(1-exponent));B^(1-exponent) tends0,so limit=23/2

Conditions: none

Because k>1,the negative power tends0.The absolute tail error is |scale|/((k−1)B^(k−1)),which is below any epsilon for sufficiently large B.Signed or zero scale is allowed;this is a universal limit,not sampled cutoffs.

Step identifiers and dependencies

Rule: improper_WHOLE_one_sided_tail_antiderivative_limit_not_samples · Uses: G001, S010

S012 · calculation

Before

Improper independently convergent tails plus zero middle := sum(11, 23/2)

After

Improper independently convergent tails plus zero middle = 45/2

Conditions: none

Substitute original roles and established intermediates exactly,without floats or treating finite tests as universal limits.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S011

S013 · implies

Before

ORIGINAL piecewise scales left=22,right=23,exponent=3;middle(-1,1) integrand0

After

negative-tail limit=11;positive-tail limit=23/2;BOTH independently finite,then ordinary sum=45/2

Conditions: none

Substitute u=-x to turn the negative tail into[1,infinity),without an extra sign;the middle contributes0.Even if the values cancel,convergence follows from two independent limit certificates,not symmetry.

Step identifiers and dependencies

Rule: improper_TWO_independent_infinite_tails_before_signed_sum · Uses: G001, S012

Reverse checks

  • S013 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S012 · premise_and_result_audit — Recompute Improper independently convergent tails plus zero middle with exact rational arithmetic, not rounded decimals.
  • S011 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S010 · premise_and_result_audit — Recompute Improper ORIGINAL positive tail exact antiderivative limit value with exact rational arithmetic, not rounded decimals.
  • S009 · premise_and_result_audit — Recompute Improper ORIGINAL positive tail exponent-minus-one times lower-power with exact rational arithmetic, not rounded decimals.
  • S008 · premise_and_result_audit — Recompute Improper ORIGINAL positive tail lower positive power step2 with exact rational arithmetic, not rounded decimals.
  • S007 · premise_and_result_audit — Recompute Improper ORIGINAL positive tail lower positive power step1 with exact rational arithmetic, not rounded decimals.
  • 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 Improper ORIGINAL negative tail after x=-u exact antiderivative limit value with exact rational arithmetic, not rounded decimals.
  • S004 · premise_and_result_audit — Recompute Improper ORIGINAL negative tail after x=-u exponent-minus-one times lower-power with exact rational arithmetic, not rounded decimals.
  • S003 · premise_and_result_audit — Recompute Improper ORIGINAL negative tail after x=-u lower positive power step2 with exact rational arithmetic, not rounded decimals.
  • S002 · premise_and_result_audit — Recompute Improper ORIGINAL negative tail after x=-u lower positive power step1 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

(x<=-1:22/abs(x)^3;-1<x<1:0;x>=1:23/x^3, (-infinity,infinity), 11, 23/2, Yes, Yes, 45/2, both_one_sided_tail_integrals_converge_independently)

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: 9d7b695dc89e654eacb3e5155e2e0bac8e82a64fe860904b223a9442fe33d221
  • candidate record SHA-256: 5237e4446d41659a28cf3b65c1b2617eca55ddc0f4c3d85e561b58a25dc5bb8f
  • semantic review receipt SHA-256: a7c0d888ade6d307703c4222c4137c78c0d2448babdcba2fa3446fe6fdd343c1
  • question-first witness SHA-256: c9571f97a37d503ad6a61034cc00108543a05c37ef246d1c4962f55136a3de02
  • Lean: NOT_RUN · human review: NOT_PERFORMED
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