Explore related knowledge and questions →

Question 33593: Cancel Only Nonzero h before Taking the Symbolic Slice Limit

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

Return to catalogue page 168

← Question derivation index · Original question batch

R0066-33593 · q-20261013-advance-20261025-r07-partial-derivative-0093

Original question and givens

Use the quadratic candidate coefficients=[5, 0, 0, 2, 1, 0] in fixed order [1,x,y,x²,x*y,y²]. Fix the other coordinate before taking a one-variable derivative. These symbolic polynomial identities do not replace a limit by one finite-difference sample or establish total differentiability of general functions. point x=0, y=0; keep y fixed. Give (coefficients,x,y,[constant,h coefficient] of the exact x-difference quotient,quotient=constant+h_coefficient*h for h≠0,limit,symbolic_limit_not_finite_difference).

  • G001 — Use the quadratic candidate coefficients=[5, 0, 0, 2, 1, 0] in fixed order [1,x,y,x²,x*y,y²]. Fix the other coordinate before taking a one-variable derivative. These symbolic polynomial identities do not replace a limit by one finite-difference sample or establish total differentiability of general functions. point x=0, y=0; keep y fixed. Give (coefficients,x,y,[constant,h coefficient] of the exact x-difference quotient,quotient=constant+h_coefficient*h for h≠0,limit,symbolic_limit_not_finite_difference).

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-mod25-partialdeep-slice-difference-quotient-limit, [coefficients, domain, operation, x, y]]

After

derived = [partialdeep-slice-difference-quotient-limit, Polynomial_partial_derivative_density]

Conditions: none

THIS source uses LOCAL-hyphen operations with exact keys/domain.Keep source field order and numeric/Boolean/string roles;integer rational texts omit/1.Original questions,English,MKOs,ASTs and statuses remain unchanged.

Step identifiers and dependencies

Rule: R66_EXACT_source_bank_keys_local_operation_domain · Uses: G001

S002 · implies

Before

source roles = [[5, 0, 0, 2, 1, 0]]

After

derived = [1, x, y, x^2, x*y, y^2]

Conditions: none

The SIX coefficients use the full[1,x,y,x²,xy,y²]basis.Hold the OTHER coordinate fixed.This supplied polynomial supports symbolic identities,not inference of a derivative from one difference sample or total differentiability of arbitrary functions.

Step identifiers and dependencies

Rule: Partial_FULL_polynomial_basis_and_fixed_other_coordinate · Uses: G001, S001

S003 · calculation

Before

Quotient ORIGINAL twice c_xx := mul(2, 2)

After

Quotient ORIGINAL twice c_xx = 4

Conditions: none

Calculate exactly from THIS step’s ORIGINAL ordered operands.Retain the SOURCE rational pre-reduction envelope separately;do not use floating values or silently widen a different bank.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S002

S004 · calculation

Before

Quotient ORIGINAL twice c_xx times x := mul(4, 0)

After

Quotient ORIGINAL twice c_xx times x = 0

Conditions: none

Calculate exactly from THIS step’s ORIGINAL ordered operands.Retain the SOURCE rational pre-reduction envelope separately;do not use floating values or silently widen a different bank.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S003

S005 · calculation

Before

Quotient ORIGINAL c_xy times fixed y := mul(1, 0)

After

Quotient ORIGINAL c_xy times fixed y = 0

Conditions: none

Calculate exactly from THIS step’s ORIGINAL ordered operands.Retain the SOURCE rational pre-reduction envelope separately;do not use floating values or silently widen a different bank.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S004

S006 · calculation

Before

Quotient ORIGINAL all linear h coefficients := sum(0, 0, 0)

After

Quotient ORIGINAL all linear h coefficients = 0

Conditions: none

Calculate exactly from THIS step’s ORIGINAL ordered operands.Retain the SOURCE rational pre-reduction envelope separately;do not use floating values or silently widen a different bank.

Step identifiers and dependencies

Rule: exact_rational_arithmetic · Uses: G001, S005

S007 · implies

Before

source roles = [[5, 0, 0, 2, 1, 0], 0, 0]

After

derived = [u(x+h,y)-u(x,y)=(0)*h+(2)*h^2]

Conditions: none

Expand and subtract ALL six original terms:constant/y/y² cancel,the x term gives c_x*h,the x² term gives2*c_xx*x*h+c_xx*h²,and xy gives c_xy*y*h.This is a symbolic identity for every h.

Step identifiers and dependencies

Rule: Partial_SYMBOLIC_difference_expand_ALL_six_terms · Uses: G001, S006

S008 · implies

Before

source roles = [0, 2, 0, 0]

After

derived = [[0, 2], 0, h!=0 before division;h->0 afterwards]

Conditions: none

Divide by h ONLY for h≠0,obtaining constant+c_xx*h.THEN polynomial continuity gives limit constant as h→0.The original quotient is undefined at h=0;never substitute0 into0/0.A finite difference is not this limit proof.

Step identifiers and dependencies

Rule: Partial_CANCEL_h_ONLY_nonzero_THEN_polynomial_limit · Uses: G001, S007

Reverse checks

  • S008 · premise_and_result_audit — Reverse-audit THIS step against its ORIGINAL ordered roles and complete premises.Accept the conclusion only under these conditions;do not invert a one-way implication or call a finite check a general formal proof.
  • S007 · premise_and_result_audit — Reverse-audit THIS step against its ORIGINAL ordered roles and complete premises.Accept the conclusion only under these conditions;do not invert a one-way implication or call a finite check a general formal proof.
  • S006 · premise_and_result_audit — Recompute Quotient ORIGINAL all linear h coefficients with exact rational arithmetic, not rounded decimals.
  • S005 · premise_and_result_audit — Recompute Quotient ORIGINAL c_xy times fixed y with exact rational arithmetic, not rounded decimals.
  • S004 · premise_and_result_audit — Recompute Quotient ORIGINAL twice c_xx times x with exact rational arithmetic, not rounded decimals.
  • S003 · premise_and_result_audit — Recompute Quotient ORIGINAL twice c_xx with exact rational arithmetic, not rounded decimals.
  • S002 · premise_and_result_audit — Reverse-audit THIS step against its ORIGINAL ordered roles and complete premises.Accept the conclusion only under these conditions;do not invert a one-way implication or call a finite check a general formal proof.
  • S001 · premise_and_result_audit — Reverse-audit THIS step against its ORIGINAL ordered roles and complete premises.Accept the conclusion only under these conditions;do not invert a one-way implication or call a finite check a general formal proof.

Result

([5, 0, 0, 2, 1, 0], 0, 0, [0, 2], quotient=constant+h_coefficient*h for h≠0, 0, symbolic_limit_not_finite_difference)

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: 516913fedee1e83b6c181abc54b251cef43f3d7b258f80e750a8e0a35fc52829
  • candidate record SHA-256: 06bb47fa5e436aeb9b474bd01cbbf8ceb277d89c3fc9fe124338d7675d7d61dd
  • semantic review receipt SHA-256: 99b4f114b2ec93164b6aa5681e0107033a240e7a3f0a8988633ba65320ede267
  • question-first witness SHA-256: d9bd3a1940da8a73f790ee3fe460c9a8523791bdbe72c8e0304e3740b66710cc
  • Lean: NOT_RUN · human review: NOT_PERFORMED
Same-source full JSON