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Question 28697: Average Rate of a Vertex-Form Quadratic

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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R0056-28697 · q-20261005-advance-20261006-r03-rate-of-change-0097

Original question and givens

On the full real domain, let q:R→R be q(x)=(-22)(x−(9))²+(9), with a≠0. For distinct inputs 31 and 8, find the average rate of change. Give a reduced fraction with positive denominator, retaining /1 for integers.

  • G001 — On the full real domain, let q:R→R be q(x)=(-22)(x−(9))²+(9), with a≠0. For distinct inputs 31 and 8, find the average rate of change. Give a reduced fraction with positive denominator, retaining /1 for integers.

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 roles = [qf-rate-quadratic-average, quadratic_average]

After

derived = [exact_quadratic_endpoint_average_not_derivative]

Conditions: none

Use the declared scalar/set/Yes-No/fraction answer role;integer fractions retain/1.Do not add an undeclared domain or change original bilingual data,formulas or questions.

Step identifiers and dependencies

Rule: R56_source_answer_role_and_EXACT_family_interface · Uses: G001

S002 · calculation

Before

Rate ORIGINAL x1 minus x0 := sub(8, 31)

After

Rate ORIGINAL x1 minus x0 = -23

Conditions: none

Perform exact rational arithmetic on the ORIGINAL roles.SAFE bounds raw inputs only;derived integers are unbounded and never approximated by floats.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S001

S003 · calculation

Before

Rate quadratic ORIGINAL displacement0 := sub(31, 9)

After

Rate quadratic ORIGINAL displacement0 = 22

Conditions: none

Perform exact rational arithmetic on the ORIGINAL roles.SAFE bounds raw inputs only;derived integers are unbounded and never approximated by floats.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S002

S004 · calculation

Before

Rate quadratic ORIGINAL square0 := mul(22, 22)

After

Rate quadratic ORIGINAL square0 = 484

Conditions: none

Perform exact rational arithmetic on the ORIGINAL roles.SAFE bounds raw inputs only;derived integers are unbounded and never approximated by floats.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S003

S005 · calculation

Before

Rate quadratic ORIGINAL a times square0 := mul(-22, 484)

After

Rate quadratic ORIGINAL a times square0 = -10648

Conditions: none

Perform exact rational arithmetic on the ORIGINAL roles.SAFE bounds raw inputs only;derived integers are unbounded and never approximated by floats.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S004

S006 · calculation

Before

Rate quadratic ORIGINAL endpoint0 plus k := sum(-10648, 9)

After

Rate quadratic ORIGINAL endpoint0 plus k = -10639

Conditions: none

Perform exact rational arithmetic on the ORIGINAL roles.SAFE bounds raw inputs only;derived integers are unbounded and never approximated by floats.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S005

S007 · calculation

Before

Rate quadratic ORIGINAL displacement1 := sub(8, 9)

After

Rate quadratic ORIGINAL displacement1 = -1

Conditions: none

Perform exact rational arithmetic on the ORIGINAL roles.SAFE bounds raw inputs only;derived integers are unbounded and never approximated by floats.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S006

S008 · calculation

Before

Rate quadratic ORIGINAL square1 := mul(-1, -1)

After

Rate quadratic ORIGINAL square1 = 1

Conditions: none

Perform exact rational arithmetic on the ORIGINAL roles.SAFE bounds raw inputs only;derived integers are unbounded and never approximated by floats.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S007

S009 · calculation

Before

Rate quadratic ORIGINAL a times square1 := mul(-22, 1)

After

Rate quadratic ORIGINAL a times square1 = -22

Conditions: none

Perform exact rational arithmetic on the ORIGINAL roles.SAFE bounds raw inputs only;derived integers are unbounded and never approximated by floats.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S008

S010 · calculation

Before

Rate quadratic ORIGINAL endpoint1 plus k := sum(-22, 9)

After

Rate quadratic ORIGINAL endpoint1 plus k = -13

Conditions: none

Perform exact rational arithmetic on the ORIGINAL roles.SAFE bounds raw inputs only;derived integers are unbounded and never approximated by floats.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S009

S011 · implies

Before

source roles = [-22, 9, 9, 31, 8]

After

derived = [[-10639, -13], dy=a*(x1-x0)*(x1+x0-2h)]

Conditions: none

Use the WHOLE vertex-form quadratic.The k terms cancel and the square difference factors as(x1-x0)(x1+x0-2h).Symmetric endpoints can give dy=0 although a is nonzero;the function need not be constant.

Step identifiers and dependencies

Rule: Rate_WHOLE_quadratic_difference_of_squares · Uses: G001, S010

S012 · calculation

Before

Rate ORIGINAL y1 minus y0 := sub(-13, -10639)

After

Rate ORIGINAL y1 minus y0 = 10626

Conditions: none

Perform exact rational arithmetic on the ORIGINAL roles.SAFE bounds raw inputs only;derived integers are unbounded and never approximated by floats.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S011

S013 · calculation

Before

Rate ORIGINAL dy over dx := div(10626, -23)

After

Rate ORIGINAL dy over dx = -462

Conditions: none

Perform exact rational arithmetic on the ORIGINAL roles.SAFE bounds raw inputs only;derived integers are unbounded and never approximated by floats.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S012

S014 · implies

Before

source roles = [31, 8, -10639, -13, -23, 10626]

After

derived = [-462/1]

Conditions: none

Keep the SAME endpoint orientation:(y1-y0)/(x1-x0).Both differences may reverse together,not just one.The result may be negative or0;normalize a positive denominator and retain/1.This finite endpoint rate is not a general derivative certificate.

Step identifiers and dependencies

Rule: Rate_oriented_quotient_reverse_BOTH_differences · Uses: G001, S013

Reverse checks

  • S014 · premise_and_result_audit — Reverse-check EACH original datum and premise,retaining indices,signs and strict/non-strict boundaries.A correct final answer cannot replace the derivation obligations.This is candidate teaching/exact checking,not formal proof or publication clearance.
  • S013 · premise_and_result_audit — Recompute Rate ORIGINAL dy over dx with exact rational arithmetic, not rounded decimals.
  • S012 · premise_and_result_audit — Recompute Rate ORIGINAL y1 minus y0 with exact rational arithmetic, not rounded decimals.
  • S011 · premise_and_result_audit — Reverse-check EACH original datum and premise,retaining indices,signs and strict/non-strict boundaries.A correct final answer cannot replace the derivation obligations.This is candidate teaching/exact checking,not formal proof or publication clearance.
  • S010 · premise_and_result_audit — Recompute Rate quadratic ORIGINAL endpoint1 plus k with exact rational arithmetic, not rounded decimals.
  • S009 · premise_and_result_audit — Recompute Rate quadratic ORIGINAL a times square1 with exact rational arithmetic, not rounded decimals.
  • S008 · premise_and_result_audit — Recompute Rate quadratic ORIGINAL square1 with exact rational arithmetic, not rounded decimals.
  • S007 · premise_and_result_audit — Recompute Rate quadratic ORIGINAL displacement1 with exact rational arithmetic, not rounded decimals.
  • S006 · premise_and_result_audit — Recompute Rate quadratic ORIGINAL endpoint0 plus k with exact rational arithmetic, not rounded decimals.
  • S005 · premise_and_result_audit — Recompute Rate quadratic ORIGINAL a times square0 with exact rational arithmetic, not rounded decimals.
  • S004 · premise_and_result_audit — Recompute Rate quadratic ORIGINAL square0 with exact rational arithmetic, not rounded decimals.
  • S003 · premise_and_result_audit — Recompute Rate quadratic ORIGINAL displacement0 with exact rational arithmetic, not rounded decimals.
  • S002 · premise_and_result_audit — Recompute Rate ORIGINAL x1 minus x0 with exact rational arithmetic, not rounded decimals.
  • S001 · premise_and_result_audit — Reverse-check EACH original datum and premise,retaining indices,signs and strict/non-strict boundaries.A correct final answer cannot replace the derivation obligations.This is candidate teaching/exact checking,not formal proof or publication clearance.

Result

-462/1

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: 99884570a8f0e9af953a98edb2571b21c49dcb3ce438e1edf2830433ae22e6bb
  • candidate record SHA-256: 8ef7913191f0d68b4388d2de2d2220c41212ae1abd42da56ddb75c7af93e8ae7
  • semantic review receipt SHA-256: 8bbda4edbed7078634ae88342998c79bcfb95de96187fac119c3b08e0adb0bc8
  • question-first witness SHA-256: 3edafa72d63d16a22414892b55806430e0a25b15b926d04f312550179607759f
  • Lean: NOT_RUN · human review: NOT_PERFORMED
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