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Question 1987: 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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R0002-01987 · q-20261013-advance-20261020-r02-ordinary-differential-equation-0062

Original question and givens

The integer-coefficient polynomial candidate has ascending-power coefficients=[3, -1, 2, 2]. Exact checks concern only the specified point or initial conditions, not existence, uniqueness or a solution on an entire interval. At x=-1, check a*y''+b*y'+c*y=rhs with a=2≠0, b=1, c=-2, rhs=13. Give (coefficients, x, y, y', y'', a, b, c, rhs, signed residual, zero?).

  • G001 — The integer-coefficient polynomial candidate has ascending-power coefficients=[3, -1, 2, 2]. Exact checks concern only the specified point or initial conditions, not existence, uniqueness or a solution on an entire interval. At x=-1, check a*y''+b*y'+c*y=rhs with a=2≠0, b=1, c=-2, rhs=13. 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=[3, -1, 2, 2]

After

audit point x=-1

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, -1)

After

y′ coefficient at degree0 = -1

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, 2)

After

y′ coefficient at degree1 = 4

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, 4)

After

y″ coefficient at degree0 = 4

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=[3, -1, 2, 2]

After

evaluate at x=-1

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, -1)

After

y Horner multiply before degree2 = -2

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(-2, 2)

After

y Horner add degree2 = 0

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(0, -1)

After

y Horner multiply before degree1 = 0

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(0, -1)

After

y Horner add degree1 = -1

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(-1, -1)

After

y Horner multiply before degree0 = 1

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(1, 3)

After

y Horner add degree0 = 4

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=[-1, 4, 6]

After

evaluate at x=-1

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, -1)

After

y′ Horner multiply before degree1 = -6

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(-6, 4)

After

y′ Horner add degree1 = -2

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(-2, -1)

After

y′ Horner multiply before degree0 = 2

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(2, -1)

After

y′ Horner add degree0 = 1

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=[4, 12]

After

evaluate at x=-1

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, -1)

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, S019

S021 · calculation

Before

y″ Horner add degree0 := sum(-12, 4)

After

y″ Horner add degree0 = -8

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(2, -8)

After

a·y″ = -16

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(1, 1)

After

b·y′ = 1

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(-2, 4)

After

c·y = -8

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(-16, 1, -8)

After

a·y″+b·y′+c·y = -23

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(-23, 13)

After

second-order residual = -36

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=-1 is -36

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

([3, -1, 2, 2], -1, 4, 1, -8, 2, 1, -2, 13, -36, 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: 64f94d2e37234fe262e6cc37e702fb7de5655554a479c1c296e2b9bdd7f20ead
  • candidate record SHA-256: 23931443f796d55cd7256d3bdcb5ffe2c55effbf98591b0260c0d0603ab24bd1
  • semantic review receipt SHA-256: 340d74dcc6e37df6249594a0b79a9ee2af804337b7847478b3c1342af9722861
  • question-first witness SHA-256: 9a06233d190d31a16f13fb03b6c3ceba4cbb748fff6c997941f66ab1888dcca8
  • Lean: NOT_RUN · human review: NOT_PERFORMED
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