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Question 98: The Finite Expansion Includes Every k from Zero through n

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  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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P250-0098 · q-20261014-advance-20261109-r05-binomial-theorem-0048

Original question and givens

Use natural exponent n=22, including0, in a commutative coefficient setting. Give (n, coefficient_exponent_rows, boundary).

  • G001 — Use natural exponent n=22, 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=22≥0; x,y commute

After

(x+y)^22 is a finite product of 22 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

choose exactly 0 of 22 factors to contribute y

After

C(22,0)=1124000727777607680000/(1·1124000727777607680000)=1

Conditions: none

Count orderings of 22 positions and divide by reorderings within the 0 y positions and 22 x positions, giving coefficient 1.

Step identifiers and dependencies

Rule: subset_count · Uses: G001, S001

S003 · implies

Before

C(22,0)=1; choose y 0 times

After

1·x^22·y^0

Conditions: none

The x exponent is 22-0=22; the two exponents still sum to 22.

Step identifiers and dependencies

Rule: group_like_terms · Uses: G001, S002

S004 · implies

Before

choose exactly 1 of 22 factors to contribute y

After

C(22,1)=1124000727777607680000/(1·51090942171709440000)=22

Conditions: none

Count orderings of 22 positions and divide by reorderings within the 1 y positions and 21 x positions, giving coefficient 22.

Step identifiers and dependencies

Rule: subset_count · Uses: G001, S003

S005 · implies

Before

C(22,1)=22; choose y 1 times

After

22·x^21·y^1

Conditions: none

The x exponent is 22-1=21; the two exponents still sum to 22.

Step identifiers and dependencies

Rule: group_like_terms · Uses: G001, S004

S006 · implies

Before

choose exactly 2 of 22 factors to contribute y

After

C(22,2)=1124000727777607680000/(2·2432902008176640000)=231

Conditions: none

Count orderings of 22 positions and divide by reorderings within the 2 y positions and 20 x positions, giving coefficient 231.

Step identifiers and dependencies

Rule: subset_count · Uses: G001, S005

S007 · implies

Before

C(22,2)=231; choose y 2 times

After

231·x^20·y^2

Conditions: none

The x exponent is 22-2=20; the two exponents still sum to 22.

Step identifiers and dependencies

Rule: group_like_terms · Uses: G001, S006

S008 · implies

Before

choose exactly 3 of 22 factors to contribute y

After

C(22,3)=1124000727777607680000/(6·121645100408832000)=1540

Conditions: none

Count orderings of 22 positions and divide by reorderings within the 3 y positions and 19 x positions, giving coefficient 1540.

Step identifiers and dependencies

Rule: subset_count · Uses: G001, S007

S009 · implies

Before

C(22,3)=1540; choose y 3 times

After

1540·x^19·y^3

Conditions: none

The x exponent is 22-3=19; the two exponents still sum to 22.

Step identifiers and dependencies

Rule: group_like_terms · Uses: G001, S008

S010 · implies

Before

choose exactly 4 of 22 factors to contribute y

After

C(22,4)=1124000727777607680000/(24·6402373705728000)=7315

Conditions: none

Count orderings of 22 positions and divide by reorderings within the 4 y positions and 18 x positions, giving coefficient 7315.

Step identifiers and dependencies

Rule: subset_count · Uses: G001, S009

S011 · implies

Before

C(22,4)=7315; choose y 4 times

After

7315·x^18·y^4

Conditions: none

The x exponent is 22-4=18; the two exponents still sum to 22.

Step identifiers and dependencies

Rule: group_like_terms · Uses: G001, S010

S012 · implies

Before

choose exactly 5 of 22 factors to contribute y

After

C(22,5)=1124000727777607680000/(120·355687428096000)=26334

Conditions: none

Count orderings of 22 positions and divide by reorderings within the 5 y positions and 17 x positions, giving coefficient 26334.

Step identifiers and dependencies

Rule: subset_count · Uses: G001, S011

S013 · implies

Before

C(22,5)=26334; choose y 5 times

After

26334·x^17·y^5

Conditions: none

The x exponent is 22-5=17; the two exponents still sum to 22.

Step identifiers and dependencies

Rule: group_like_terms · Uses: G001, S012

S014 · implies

Before

choose exactly 6 of 22 factors to contribute y

After

C(22,6)=1124000727777607680000/(720·20922789888000)=74613

Conditions: none

Count orderings of 22 positions and divide by reorderings within the 6 y positions and 16 x positions, giving coefficient 74613.

Step identifiers and dependencies

Rule: subset_count · Uses: G001, S013

S015 · implies

Before

C(22,6)=74613; choose y 6 times

After

74613·x^16·y^6

Conditions: none

The x exponent is 22-6=16; the two exponents still sum to 22.

Step identifiers and dependencies

Rule: group_like_terms · Uses: G001, S014

S016 · implies

Before

choose exactly 7 of 22 factors to contribute y

After

C(22,7)=1124000727777607680000/(5040·1307674368000)=170544

Conditions: none

Count orderings of 22 positions and divide by reorderings within the 7 y positions and 15 x positions, giving coefficient 170544.

Step identifiers and dependencies

Rule: subset_count · Uses: G001, S015

S017 · implies

Before

C(22,7)=170544; choose y 7 times

After

170544·x^15·y^7

Conditions: none

The x exponent is 22-7=15; the two exponents still sum to 22.

Step identifiers and dependencies

Rule: group_like_terms · Uses: G001, S016

S018 · implies

Before

choose exactly 8 of 22 factors to contribute y

After

C(22,8)=1124000727777607680000/(40320·87178291200)=319770

Conditions: none

Count orderings of 22 positions and divide by reorderings within the 8 y positions and 14 x positions, giving coefficient 319770.

Step identifiers and dependencies

Rule: subset_count · Uses: G001, S017

S019 · implies

Before

C(22,8)=319770; choose y 8 times

After

319770·x^14·y^8

Conditions: none

The x exponent is 22-8=14; the two exponents still sum to 22.

Step identifiers and dependencies

Rule: group_like_terms · Uses: G001, S018

S020 · implies

Before

choose exactly 9 of 22 factors to contribute y

After

C(22,9)=1124000727777607680000/(362880·6227020800)=497420

Conditions: none

Count orderings of 22 positions and divide by reorderings within the 9 y positions and 13 x positions, giving coefficient 497420.

Step identifiers and dependencies

Rule: subset_count · Uses: G001, S019

S021 · implies

Before

C(22,9)=497420; choose y 9 times

After

497420·x^13·y^9

Conditions: none

The x exponent is 22-9=13; the two exponents still sum to 22.

Step identifiers and dependencies

Rule: group_like_terms · Uses: G001, S020

S022 · implies

Before

choose exactly 10 of 22 factors to contribute y

After

C(22,10)=1124000727777607680000/(3628800·479001600)=646646

Conditions: none

Count orderings of 22 positions and divide by reorderings within the 10 y positions and 12 x positions, giving coefficient 646646.

Step identifiers and dependencies

Rule: subset_count · Uses: G001, S021

S023 · implies

Before

C(22,10)=646646; choose y 10 times

After

646646·x^12·y^10

Conditions: none

The x exponent is 22-10=12; the two exponents still sum to 22.

Step identifiers and dependencies

Rule: group_like_terms · Uses: G001, S022

S024 · implies

Before

choose exactly 11 of 22 factors to contribute y

After

C(22,11)=1124000727777607680000/(39916800·39916800)=705432

Conditions: none

Count orderings of 22 positions and divide by reorderings within the 11 y positions and 11 x positions, giving coefficient 705432.

Step identifiers and dependencies

Rule: subset_count · Uses: G001, S023

S025 · implies

Before

C(22,11)=705432; choose y 11 times

After

705432·x^11·y^11

Conditions: none

The x exponent is 22-11=11; the two exponents still sum to 22.

Step identifiers and dependencies

Rule: group_like_terms · Uses: G001, S024

S026 · implies

Before

choose exactly 12 of 22 factors to contribute y

After

C(22,12)=1124000727777607680000/(479001600·3628800)=646646

Conditions: none

Count orderings of 22 positions and divide by reorderings within the 12 y positions and 10 x positions, giving coefficient 646646.

Step identifiers and dependencies

Rule: subset_count · Uses: G001, S025

S027 · implies

Before

C(22,12)=646646; choose y 12 times

After

646646·x^10·y^12

Conditions: none

The x exponent is 22-12=10; the two exponents still sum to 22.

Step identifiers and dependencies

Rule: group_like_terms · Uses: G001, S026

S028 · implies

Before

choose exactly 13 of 22 factors to contribute y

After

C(22,13)=1124000727777607680000/(6227020800·362880)=497420

Conditions: none

Count orderings of 22 positions and divide by reorderings within the 13 y positions and 9 x positions, giving coefficient 497420.

Step identifiers and dependencies

Rule: subset_count · Uses: G001, S027

S029 · implies

Before

C(22,13)=497420; choose y 13 times

After

497420·x^9·y^13

Conditions: none

The x exponent is 22-13=9; the two exponents still sum to 22.

Step identifiers and dependencies

Rule: group_like_terms · Uses: G001, S028

S030 · implies

Before

choose exactly 14 of 22 factors to contribute y

After

C(22,14)=1124000727777607680000/(87178291200·40320)=319770

Conditions: none

Count orderings of 22 positions and divide by reorderings within the 14 y positions and 8 x positions, giving coefficient 319770.

Step identifiers and dependencies

Rule: subset_count · Uses: G001, S029

S031 · implies

Before

C(22,14)=319770; choose y 14 times

After

319770·x^8·y^14

Conditions: none

The x exponent is 22-14=8; the two exponents still sum to 22.

Step identifiers and dependencies

Rule: group_like_terms · Uses: G001, S030

S032 · implies

Before

choose exactly 15 of 22 factors to contribute y

After

C(22,15)=1124000727777607680000/(1307674368000·5040)=170544

Conditions: none

Count orderings of 22 positions and divide by reorderings within the 15 y positions and 7 x positions, giving coefficient 170544.

Step identifiers and dependencies

Rule: subset_count · Uses: G001, S031

S033 · implies

Before

C(22,15)=170544; choose y 15 times

After

170544·x^7·y^15

Conditions: none

The x exponent is 22-15=7; the two exponents still sum to 22.

Step identifiers and dependencies

Rule: group_like_terms · Uses: G001, S032

S034 · implies

Before

choose exactly 16 of 22 factors to contribute y

After

C(22,16)=1124000727777607680000/(20922789888000·720)=74613

Conditions: none

Count orderings of 22 positions and divide by reorderings within the 16 y positions and 6 x positions, giving coefficient 74613.

Step identifiers and dependencies

Rule: subset_count · Uses: G001, S033

S035 · implies

Before

C(22,16)=74613; choose y 16 times

After

74613·x^6·y^16

Conditions: none

The x exponent is 22-16=6; the two exponents still sum to 22.

Step identifiers and dependencies

Rule: group_like_terms · Uses: G001, S034

S036 · implies

Before

choose exactly 17 of 22 factors to contribute y

After

C(22,17)=1124000727777607680000/(355687428096000·120)=26334

Conditions: none

Count orderings of 22 positions and divide by reorderings within the 17 y positions and 5 x positions, giving coefficient 26334.

Step identifiers and dependencies

Rule: subset_count · Uses: G001, S035

S037 · implies

Before

C(22,17)=26334; choose y 17 times

After

26334·x^5·y^17

Conditions: none

The x exponent is 22-17=5; the two exponents still sum to 22.

Step identifiers and dependencies

Rule: group_like_terms · Uses: G001, S036

S038 · implies

Before

choose exactly 18 of 22 factors to contribute y

After

C(22,18)=1124000727777607680000/(6402373705728000·24)=7315

Conditions: none

Count orderings of 22 positions and divide by reorderings within the 18 y positions and 4 x positions, giving coefficient 7315.

Step identifiers and dependencies

Rule: subset_count · Uses: G001, S037

S039 · implies

Before

C(22,18)=7315; choose y 18 times

After

7315·x^4·y^18

Conditions: none

The x exponent is 22-18=4; the two exponents still sum to 22.

Step identifiers and dependencies

Rule: group_like_terms · Uses: G001, S038

S040 · implies

Before

choose exactly 19 of 22 factors to contribute y

After

C(22,19)=1124000727777607680000/(121645100408832000·6)=1540

Conditions: none

Count orderings of 22 positions and divide by reorderings within the 19 y positions and 3 x positions, giving coefficient 1540.

Step identifiers and dependencies

Rule: subset_count · Uses: G001, S039

S041 · implies

Before

C(22,19)=1540; choose y 19 times

After

1540·x^3·y^19

Conditions: none

The x exponent is 22-19=3; the two exponents still sum to 22.

Step identifiers and dependencies

Rule: group_like_terms · Uses: G001, S040

S042 · implies

Before

choose exactly 20 of 22 factors to contribute y

After

C(22,20)=1124000727777607680000/(2432902008176640000·2)=231

Conditions: none

Count orderings of 22 positions and divide by reorderings within the 20 y positions and 2 x positions, giving coefficient 231.

Step identifiers and dependencies

Rule: subset_count · Uses: G001, S041

S043 · implies

Before

C(22,20)=231; choose y 20 times

After

231·x^2·y^20

Conditions: none

The x exponent is 22-20=2; the two exponents still sum to 22.

Step identifiers and dependencies

Rule: group_like_terms · Uses: G001, S042

S044 · implies

Before

choose exactly 21 of 22 factors to contribute y

After

C(22,21)=1124000727777607680000/(51090942171709440000·1)=22

Conditions: none

Count orderings of 22 positions and divide by reorderings within the 21 y positions and 1 x positions, giving coefficient 22.

Step identifiers and dependencies

Rule: subset_count · Uses: G001, S043

S045 · implies

Before

C(22,21)=22; choose y 21 times

After

22·x^1·y^21

Conditions: none

The x exponent is 22-21=1; the two exponents still sum to 22.

Step identifiers and dependencies

Rule: group_like_terms · Uses: G001, S044

S046 · implies

Before

choose exactly 22 of 22 factors to contribute y

After

C(22,22)=1124000727777607680000/(1124000727777607680000·1)=1

Conditions: none

Count orderings of 22 positions and divide by reorderings within the 22 y positions and 0 x positions, giving coefficient 1.

Step identifiers and dependencies

Rule: subset_count · Uses: G001, S045

S047 · implies

Before

C(22,22)=1; choose y 22 times

After

1·x^0·y^22

Conditions: none

The x exponent is 22-22=0; the two exponents still sum to 22.

Step identifiers and dependencies

Rule: group_like_terms · Uses: G001, S046

S048 · implies

Before

all k=0 through 22 have been accounted for

After

(x+y)^22=1·x^22·y^0 + 22·x^21·y^1 + 231·x^20·y^2 + 1540·x^19·y^3 + 7315·x^18·y^4 + 26334·x^17·y^5 + 74613·x^16·y^6 + 170544·x^15·y^7 + 319770·x^14·y^8 + 497420·x^13·y^9 + 646646·x^12·y^10 + 705432·x^11·y^11 + 646646·x^10·y^12 + 497420·x^9·y^13 + 319770·x^8·y^14 + 170544·x^7·y^15 + 74613·x^6·y^16 + 26334·x^5·y^17 + 7315·x^4·y^18 + 1540·x^3·y^19 + 231·x^2·y^20 + 22·x^1·y^21 + 1·x^0·y^22

Conditions: none

Every x/y choice belongs to exactly one k class, so this is the complete finite expansion, not just endpoint terms.

Step identifiers and dependencies

Rule: collect_all_terms · Uses: G001, S047

Reverse checks

  • S048 · premise_and_result_audit — There are n+1 coefficient positions, with the complete range of k retained.
  • S047 · premise_and_result_audit — The answer row is [k,coefficient,x exponent,y exponent]; do not swap the exponent columns.
  • S046 · premise_and_result_audit — Check the coefficient independently with the integer Pascal recurrence, not approximate factorials.
  • S045 · premise_and_result_audit — The answer row is [k,coefficient,x exponent,y exponent]; do not swap the exponent columns.
  • S044 · premise_and_result_audit — Check the coefficient independently with the integer Pascal recurrence, not approximate factorials.
  • S043 · premise_and_result_audit — The answer row is [k,coefficient,x exponent,y exponent]; do not swap the exponent columns.
  • S042 · premise_and_result_audit — Check the coefficient independently with the integer Pascal recurrence, not approximate factorials.
  • S041 · premise_and_result_audit — The answer row is [k,coefficient,x exponent,y exponent]; do not swap the exponent columns.
  • S040 · premise_and_result_audit — Check the coefficient independently with the integer Pascal recurrence, not approximate factorials.
  • S039 · premise_and_result_audit — The answer row is [k,coefficient,x exponent,y exponent]; do not swap the exponent columns.
  • S038 · premise_and_result_audit — Check the coefficient independently with the integer Pascal recurrence, not approximate factorials.
  • S037 · premise_and_result_audit — The answer row is [k,coefficient,x exponent,y exponent]; do not swap the exponent columns.
  • S036 · premise_and_result_audit — Check the coefficient independently with the integer Pascal recurrence, not approximate factorials.
  • S035 · premise_and_result_audit — The answer row is [k,coefficient,x exponent,y exponent]; do not swap the exponent columns.
  • S034 · premise_and_result_audit — Check the coefficient independently with the integer Pascal recurrence, not approximate factorials.
  • S033 · premise_and_result_audit — The answer row is [k,coefficient,x exponent,y exponent]; do not swap the exponent columns.
  • S032 · premise_and_result_audit — Check the coefficient independently with the integer Pascal recurrence, not approximate factorials.
  • S031 · premise_and_result_audit — The answer row is [k,coefficient,x exponent,y exponent]; do not swap the exponent columns.
  • S030 · premise_and_result_audit — Check the coefficient independently with the integer Pascal recurrence, not approximate factorials.
  • S029 · premise_and_result_audit — The answer row is [k,coefficient,x exponent,y exponent]; do not swap the exponent columns.
  • S028 · premise_and_result_audit — Check the coefficient independently with the integer Pascal recurrence, not approximate factorials.
  • S027 · premise_and_result_audit — The answer row is [k,coefficient,x exponent,y exponent]; do not swap the exponent columns.
  • S026 · premise_and_result_audit — Check the coefficient independently with the integer Pascal recurrence, not approximate factorials.
  • S025 · premise_and_result_audit — The answer row is [k,coefficient,x exponent,y exponent]; do not swap the exponent columns.
  • S024 · premise_and_result_audit — Check the coefficient independently with the integer Pascal recurrence, not approximate factorials.
  • S023 · premise_and_result_audit — The answer row is [k,coefficient,x exponent,y exponent]; do not swap the exponent columns.
  • S022 · premise_and_result_audit — Check the coefficient independently with the integer Pascal recurrence, not approximate factorials.
  • S021 · premise_and_result_audit — The answer row is [k,coefficient,x exponent,y exponent]; do not swap the exponent columns.
  • S020 · premise_and_result_audit — Check the coefficient independently with the integer Pascal recurrence, not approximate factorials.
  • S019 · premise_and_result_audit — The answer row is [k,coefficient,x exponent,y exponent]; do not swap the exponent columns.
  • S018 · premise_and_result_audit — Check the coefficient independently with the integer Pascal recurrence, not approximate factorials.
  • S017 · premise_and_result_audit — The answer row is [k,coefficient,x exponent,y exponent]; do not swap the exponent columns.
  • S016 · premise_and_result_audit — Check the coefficient independently with the integer Pascal recurrence, not approximate factorials.
  • S015 · premise_and_result_audit — The answer row is [k,coefficient,x exponent,y exponent]; do not swap the exponent columns.
  • S014 · premise_and_result_audit — Check the coefficient independently with the integer Pascal recurrence, not approximate factorials.
  • S013 · premise_and_result_audit — The answer row is [k,coefficient,x exponent,y exponent]; do not swap the exponent columns.
  • S012 · premise_and_result_audit — Check the coefficient independently with the integer Pascal recurrence, not approximate factorials.
  • S011 · premise_and_result_audit — The answer row is [k,coefficient,x exponent,y exponent]; do not swap the exponent columns.
  • S010 · premise_and_result_audit — Check the coefficient independently with the integer Pascal recurrence, not approximate factorials.
  • S009 · premise_and_result_audit — The answer row is [k,coefficient,x exponent,y exponent]; do not swap the exponent columns.
  • S008 · premise_and_result_audit — Check the coefficient independently with the integer Pascal recurrence, not approximate factorials.
  • S007 · premise_and_result_audit — The answer row is [k,coefficient,x exponent,y exponent]; do not swap the exponent columns.
  • S006 · premise_and_result_audit — Check the coefficient independently with the integer Pascal recurrence, not approximate factorials.
  • S005 · premise_and_result_audit — The answer row is [k,coefficient,x exponent,y exponent]; do not swap the exponent columns.
  • S004 · premise_and_result_audit — Check the coefficient independently with the integer Pascal recurrence, not approximate factorials.
  • S003 · premise_and_result_audit — The answer row is [k,coefficient,x exponent,y exponent]; do not swap the exponent columns.
  • S002 · premise_and_result_audit — Check the coefficient independently with the integer Pascal recurrence, not approximate factorials.
  • S001 · premise_and_result_audit — This is not an infinite expansion for a noninteger power or a claim for noncommuting multiplication.

Result

(22, [[0, 1, 22, 0], [1, 22, 21, 1], [2, 231, 20, 2], [3, 1540, 19, 3], [4, 7315, 18, 4], [5, 26334, 17, 5], [6, 74613, 16, 6], [7, 170544, 15, 7], [8, 319770, 14, 8], [9, 497420, 13, 9], [10, 646646, 12, 10], [11, 705432, 11, 11], [12, 646646, 10, 12], [13, 497420, 9, 13], [14, 319770, 8, 14], [15, 170544, 7, 15], [16, 74613, 6, 16], [17, 26334, 5, 17], [18, 7315, 4, 18], [19, 1540, 3, 19], [20, 231, 2, 20], [21, 22, 1, 21], [22, 1, 0, 22]], complete_k_zero_through_n_coefficients)

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

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