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Question 76: The Finite Expansion Includes Every k from Zero through n

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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P250-0076 · q-20261014-advance-20261109-r05-binomial-theorem-0026

Original question and givens

Use natural exponent n=0, including0, in a commutative coefficient setting. Give (n, coefficient_exponent_rows, boundary).

  • G001 — Use natural exponent n=0, including0, in a commutative coefficient setting. Give (n, coefficient_exponent_rows, boundary).

Definition and scope

n is a nonnegative integer and x,y commute. For n=0 use the polynomial empty-product identity.

Step-by-step derivation

S001 · implies

Before

n=0≥0; x,y commute

After

(x+y)^0 is a finite product of 0 factors

Conditions: none

Choose x or y from each factor; commutativity permits grouping products by the number of y choices.

Step identifiers and dependencies

Rule: finite_product · Uses: G001

S002 · implies

Before

a product with zero factors in the polynomial ring

After

empty product = multiplicative identity = 1

Conditions: none

A finite product of zero factors is defined as the multiplicative identity, so the entire polynomial is the constant 1.

Step identifiers and dependencies

Rule: empty_product_convention · Uses: G001, S001

S003 · implies

Before

choose exactly 0 of 0 factors to contribute y

After

C(0,0)=1/(1·1)=1

Conditions: none

Count orderings of 0 positions and divide by reorderings within the 0 y positions and 0 x positions, giving coefficient 1.

Step identifiers and dependencies

Rule: subset_count · Uses: G001, S002

S004 · implies

Before

C(0,0)=1; choose y 0 times

After

1·x^0·y^0

Conditions: none

The x exponent is 0-0=0; the two exponents still sum to 0.

Step identifiers and dependencies

Rule: group_like_terms · Uses: G001, S003

S005 · implies

Before

all k=0 through 0 have been accounted for

After

(x+y)^0=1·x^0·y^0

Conditions: none

For n=0 the empty product is 1. The table's x^0 y^0 denotes the constant monomial, not an arithmetic evaluation of 0^0 at x=y=0.

Step identifiers and dependencies

Rule: collect_all_terms · Uses: G001, S004

Reverse checks

  • S005 · premise_and_result_audit — There are n+1 coefficient positions, with the complete range of k retained.
  • S004 · premise_and_result_audit — The answer row is [k,coefficient,x exponent,y exponent]; do not swap the exponent columns.
  • S003 · premise_and_result_audit — Check the coefficient independently with the integer Pascal recurrence, not approximate factorials.
  • S002 · premise_and_result_audit — This polynomial empty-product convention does not assign a separate arithmetic value to the number 0^0.
  • S001 · premise_and_result_audit — This is not an infinite expansion for a noninteger power or a claim for noncommuting multiplication.

Result

(0, [[0, 1, 0, 0]], constant_one_boundary)

The full expansion consists of all displayed monomials, in the same order as the answer rows.

This question review and source binding

Review date: 2026-10-24

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: 3ab6f1fad6c6b2731837e8c6140d5184db5ed2bb90ec471cbad328ce1196a4d5
  • candidate record SHA-256: c4bae52f73f176801dad06167ec0086634c8fc560736f1d4773ccbb50e82e07c
  • semantic review receipt SHA-256: 4727d1bd957a9b7f6cadb7972ddb5ab80a31f5259dc5394c1dff2b71944ed36b
  • question-first witness SHA-256: 51e18649133238ac992229f6e16542a5f3af53ca73b2262ab0524508ea937dee
  • Lean: NOT_RUN · human review: NOT_PERFORMED
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