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Question 1990: One-Point Residual with a Nonzero Second-Order Coefficient

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

R0002-01990 · q-20261013-advance-20261020-r02-ordinary-differential-equation-0065

Original question and givens

The integer-coefficient polynomial candidate has ascending-power coefficients=[6, 2, -3, 2]. Exact checks concern only the specified point or initial conditions, not existence, uniqueness or a solution on an entire interval. At x=2, check a*y''+b*y'+c*y=rhs with a=5≠0, b=-3, c=1, rhs=22. Give (coefficients, x, y, y', y'', a, b, c, rhs, signed residual, zero?).

  • G001 — The integer-coefficient polynomial candidate has ascending-power coefficients=[6, 2, -3, 2]. Exact checks concern only the specified point or initial conditions, not existence, uniqueness or a solution on an entire interval. At x=2, check a*y''+b*y'+c*y=rhs with a=5≠0, b=-3, c=1, rhs=22. Give (coefficients, x, y, y', y'', a, b, c, rhs, signed residual, zero?).

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

candidate y ascending coefficients=[6, 2, -3, 2]

After

audit point x=2

Conditions: none

Retain the original coefficient list,including top zero terms,and audit only the specified polynomial candidate and point.

Step identifiers and dependencies

Rule: polynomial_candidate_domain · Uses: G001

S002 · calculation

Before

y′ coefficient at degree0 := mul(1, 2)

After

y′ coefficient at degree0 = 2

Conditions: none

Multiply by the original degree and lower it by1;the constant term differentiates to0.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S001

S003 · calculation

Before

y′ coefficient at degree1 := mul(2, -3)

After

y′ coefficient at degree1 = -6

Conditions: none

Multiply by the original degree and lower it by1;the constant term differentiates to0.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S002

S004 · calculation

Before

y′ coefficient at degree2 := mul(3, 2)

After

y′ coefficient at degree2 = 6

Conditions: none

Multiply by the original degree and lower it by1;the constant term differentiates to0.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S003

S005 · calculation

Before

y″ coefficient at degree0 := mul(1, -6)

After

y″ coefficient at degree0 = -6

Conditions: none

Multiply by the original degree and lower it by1;the constant term differentiates to0.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S004

S006 · calculation

Before

y″ coefficient at degree1 := mul(2, 6)

After

y″ coefficient at degree1 = 12

Conditions: none

Multiply by the original degree and lower it by1;the constant term differentiates to0.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S005

S007 · implies

Before

y ascending coefficients=[6, 2, -3, 2]

After

evaluate at x=2

Conditions: none

Evaluate ascending coefficients by Horner from the highest nonzero term down;ignoring redundant top zero terms changes neither the function nor the retained original list.

Step identifiers and dependencies

Rule: polynomial_evaluation_order · Uses: G001, S006

S008 · calculation

Before

y Horner multiply before degree2 := mul(2, 2)

After

y Horner multiply before degree2 = 4

Conditions: none

Multiply by the same evaluation point first.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S007

S009 · calculation

Before

y Horner add degree2 := sum(4, -3)

After

y Horner add degree2 = 1

Conditions: none

Then add the full coefficient at this position.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S008

S010 · calculation

Before

y Horner multiply before degree1 := mul(1, 2)

After

y Horner multiply before degree1 = 2

Conditions: none

Multiply by the same evaluation point first.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S009

S011 · calculation

Before

y Horner add degree1 := sum(2, 2)

After

y Horner add degree1 = 4

Conditions: none

Then add the full coefficient at this position.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S010

S012 · calculation

Before

y Horner multiply before degree0 := mul(4, 2)

After

y Horner multiply before degree0 = 8

Conditions: none

Multiply by the same evaluation point first.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S011

S013 · calculation

Before

y Horner add degree0 := sum(8, 6)

After

y Horner add degree0 = 14

Conditions: none

Then add the full coefficient at this position.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S012

S014 · implies

Before

y′ ascending coefficients=[2, -6, 6]

After

evaluate at x=2

Conditions: none

Evaluate ascending coefficients by Horner from the highest nonzero term down;ignoring redundant top zero terms changes neither the function nor the retained original list.

Step identifiers and dependencies

Rule: polynomial_evaluation_order · Uses: G001, S013

S015 · calculation

Before

y′ Horner multiply before degree1 := mul(6, 2)

After

y′ Horner multiply before degree1 = 12

Conditions: none

Multiply by the same evaluation point first.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S014

S016 · calculation

Before

y′ Horner add degree1 := sum(12, -6)

After

y′ Horner add degree1 = 6

Conditions: none

Then add the full coefficient at this position.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S015

S017 · calculation

Before

y′ Horner multiply before degree0 := mul(6, 2)

After

y′ Horner multiply before degree0 = 12

Conditions: none

Multiply by the same evaluation point first.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S016

S018 · calculation

Before

y′ Horner add degree0 := sum(12, 2)

After

y′ Horner add degree0 = 14

Conditions: none

Then add the full coefficient at this position.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S017

S019 · implies

Before

y″ ascending coefficients=[-6, 12]

After

evaluate at x=2

Conditions: none

Evaluate ascending coefficients by Horner from the highest nonzero term down;ignoring redundant top zero terms changes neither the function nor the retained original list.

Step identifiers and dependencies

Rule: polynomial_evaluation_order · Uses: G001, S018

S020 · calculation

Before

y″ Horner multiply before degree0 := mul(12, 2)

After

y″ Horner multiply before degree0 = 24

Conditions: none

Multiply by the same evaluation point first.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S019

S021 · calculation

Before

y″ Horner add degree0 := sum(24, -6)

After

y″ Horner add degree0 = 18

Conditions: none

Then add the full coefficient at this position.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S020

S022 · calculation

Before

a·y″ := mul(5, 18)

After

a·y″ = 90

Conditions: none

Multiply each derivative by its own original equation coefficient.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S021

S023 · calculation

Before

b·y′ := mul(-3, 14)

After

b·y′ = -42

Conditions: none

Multiply each derivative by its own original equation coefficient.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S022

S024 · calculation

Before

c·y := mul(1, 14)

After

c·y = 14

Conditions: none

Multiply each derivative by its own original equation coefficient.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S023

S025 · calculation

Before

a·y″+b·y′+c·y := sum(90, -42, 14)

After

a·y″+b·y′+c·y = 62

Conditions: none

Sum all three terms before comparing with rhs.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S024

S026 · calculation

Before

second-order residual := sub(62, 22)

After

second-order residual = 40

Conditions: none

Compute the residual with the same left-minus-right sign convention.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S025

S027 · implies

Before

residual at x=2 is 40

After

equation holds at this point: No

Conditions: none

This decides the equation at this point only;a zero residual at one point is not a solution on all reals.

Step identifiers and dependencies

Rule: point_residual_verdict · Uses: G001, S026

S028 · implies

Before

global solution would require the residual identity on the declared domain

After

no automatic existence,uniqueness or global-solution claim

Conditions: none

Equation order depends on the nonzero leading derivative coefficient,not the candidate polynomial's degree;no general existence-uniqueness theorem is invoked.

Step identifiers and dependencies

Rule: ODE_scope_guard · Uses: G001, S027

Reverse checks

  • S028 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S027 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S026 · premise_and_result_audit — Recompute second-order residual with exact rational arithmetic, not rounded decimals.
  • S025 · premise_and_result_audit — Recompute a·y″+b·y′+c·y with exact rational arithmetic, not rounded decimals.
  • S024 · premise_and_result_audit — Recompute c·y with exact rational arithmetic, not rounded decimals.
  • S023 · premise_and_result_audit — Recompute b·y′ with exact rational arithmetic, not rounded decimals.
  • S022 · premise_and_result_audit — Recompute a·y″ with exact rational arithmetic, not rounded decimals.
  • S021 · premise_and_result_audit — Recompute y″ Horner add degree0 with exact rational arithmetic, not rounded decimals.
  • S020 · premise_and_result_audit — Recompute y″ Horner multiply before degree0 with exact rational arithmetic, not rounded decimals.
  • S019 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S018 · premise_and_result_audit — Recompute y′ Horner add degree0 with exact rational arithmetic, not rounded decimals.
  • S017 · premise_and_result_audit — Recompute y′ Horner multiply before degree0 with exact rational arithmetic, not rounded decimals.
  • S016 · premise_and_result_audit — Recompute y′ Horner add degree1 with exact rational arithmetic, not rounded decimals.
  • S015 · premise_and_result_audit — Recompute y′ Horner multiply before degree1 with exact rational arithmetic, not rounded decimals.
  • S014 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
  • S013 · premise_and_result_audit — Recompute y Horner add degree0 with exact rational arithmetic, not rounded decimals.
  • S012 · premise_and_result_audit — Recompute y Horner multiply before degree0 with exact rational arithmetic, not rounded decimals.
  • S011 · premise_and_result_audit — Recompute y Horner add degree1 with exact rational arithmetic, not rounded decimals.
  • S010 · premise_and_result_audit — Recompute y Horner multiply before degree1 with exact rational arithmetic, not rounded decimals.
  • S009 · premise_and_result_audit — Recompute y Horner add degree2 with exact rational arithmetic, not rounded decimals.
  • S008 · premise_and_result_audit — Recompute y Horner multiply before degree2 with exact rational arithmetic, not rounded decimals.
  • 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 — Recompute y″ coefficient at degree1 with exact rational arithmetic, not rounded decimals.
  • S005 · premise_and_result_audit — Recompute y″ coefficient at degree0 with exact rational arithmetic, not rounded decimals.
  • S004 · premise_and_result_audit — Recompute y′ coefficient at degree2 with exact rational arithmetic, not rounded decimals.
  • S003 · premise_and_result_audit — Recompute y′ coefficient at degree1 with exact rational arithmetic, not rounded decimals.
  • S002 · premise_and_result_audit — Recompute y′ coefficient at degree0 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

([6, 2, -3, 2], 2, 14, 14, 18, 5, -3, 1, 22, 40, No)

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: e27ca31bf033eefdeb3213b547e99a4ec0fbfa8fe6642025f36a2a074ab9054a
  • candidate record SHA-256: 627d22fc35b7f8d7cf66b4c7230e093f827b1f225fa86821494b6724ba7cb812
  • semantic review receipt SHA-256: 340d74dcc6e37df6249594a0b79a9ee2af804337b7847478b3c1342af9722861
  • question-first witness SHA-256: 9a06233d190d31a16f13fb03b6c3ceba4cbb748fff6c997941f66ab1888dcca8
  • Lean: NOT_RUN · human review: NOT_PERFORMED
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