Question 2900: Bijectivity of a Finite Total Function

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Original question and givens
Definition and scope
Step-by-step derivation
Reverse checks
Result
This question review and source binding

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R0004-02900 · q-20261004-advance-20261005-r03-bijective-0025

Original question and givens

The declared total function f:A→B has A={-6, -5, -4, -3, -2, -1, 0}, B={-8, -7, -6, -5, -4, -3, -2, -1}, and table {(-6, -1), (-5, -1), (-4, -2), (-3, -2), (-2, -3), (-1, -3), (0, -4)}. Is f both injective and surjective? Decide bijectivity from the actual table.

G001 — The declared total function f:A→B has A={-6, -5, -4, -3, -2, -1, 0}, B={-8, -7, -6, -5, -4, -3, -2, -1}, and table {(-6, -1), (-5, -1), (-4, -2), (-3, -2), (-2, -3), (-1, -3), (0, -4)}. Is f both injective and surjective? Decide bijectivity from the actual table.

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.

mko-bijective

Step-by-step derivation

S001 · implies

Before

A=[-6, -5, -4, -3, -2, -1, 0]; B=[-8, -7, -6, -5, -4, -3, -2, -1]; table=[[-6, -1], [-5, -1], [-4, -2], [-3, -2], [-2, -3], [-1, -3], [0, -4]]

After

legal total function on the declared A→B

Conditions: none

First check exactly one table value for every A-element,and no input outside A or output outside B.Injectivity and surjectivity refer to this declared codomain.

Step identifiers and dependencies

Rule: declared_total_function · Uses: G001

S002 · implies

Before

input -6

After

f(-6)=-1∈B; exactly one listed value

Conditions: none

Audit each domain row of the total function,not just set cardinalities.

Step identifiers and dependencies

Rule: total_function_row · Uses: G001, S001

S003 · implies

Before

input -5

After

f(-5)=-1∈B; exactly one listed value

Conditions: none

Audit each domain row of the total function,not just set cardinalities.

Step identifiers and dependencies

Rule: total_function_row · Uses: G001, S002

S004 · implies

Before

input -4

After

f(-4)=-2∈B; exactly one listed value

Conditions: none

Audit each domain row of the total function,not just set cardinalities.

Step identifiers and dependencies

Rule: total_function_row · Uses: G001, S003

S005 · implies

Before

input -3

After

f(-3)=-2∈B; exactly one listed value

Conditions: none

Audit each domain row of the total function,not just set cardinalities.

Step identifiers and dependencies

Rule: total_function_row · Uses: G001, S004

S006 · implies

Before

input -2

After

f(-2)=-3∈B; exactly one listed value

Conditions: none

Audit each domain row of the total function,not just set cardinalities.

Step identifiers and dependencies

Rule: total_function_row · Uses: G001, S005

S007 · implies

Before

input -1

After

f(-1)=-3∈B; exactly one listed value

Conditions: none

Audit each domain row of the total function,not just set cardinalities.

Step identifiers and dependencies

Rule: total_function_row · Uses: G001, S006

S008 · implies

Before

input 0

After

f(0)=-4∈B; exactly one listed value

Conditions: none

Audit each domain row of the total function,not just set cardinalities.

Step identifiers and dependencies

Rule: total_function_row · Uses: G001, S007

S009 · implies

Before

target -8; all source rows examined

After

fiber=[]; size=0

Conditions: none

List every preimage of this target;an unhit codomain element still has an empty fiber of size0.

Step identifiers and dependencies

Rule: complete_codomain_fiber · Uses: G001, S008

S010 · implies

Before

target -7; all source rows examined

After

fiber=[]; size=0

Conditions: none

List every preimage of this target;an unhit codomain element still has an empty fiber of size0.

Step identifiers and dependencies

Rule: complete_codomain_fiber · Uses: G001, S009

S011 · implies

Before

target -6; all source rows examined

After

fiber=[]; size=0

Conditions: none

List every preimage of this target;an unhit codomain element still has an empty fiber of size0.

Step identifiers and dependencies

Rule: complete_codomain_fiber · Uses: G001, S010

S012 · implies

Before

target -5; all source rows examined

After

fiber=[]; size=0

Conditions: none

List every preimage of this target;an unhit codomain element still has an empty fiber of size0.

Step identifiers and dependencies

Rule: complete_codomain_fiber · Uses: G001, S011

S013 · implies

Before

target -4; all source rows examined

After

fiber=[0]; size=1

Conditions: none

List every preimage of this target;an unhit codomain element still has an empty fiber of size0.

Step identifiers and dependencies

Rule: complete_codomain_fiber · Uses: G001, S012

S014 · implies

Before

target -3; all source rows examined

After

fiber=[-2, -1]; size=2

Conditions: none

List every preimage of this target;an unhit codomain element still has an empty fiber of size0.

Step identifiers and dependencies

Rule: complete_codomain_fiber · Uses: G001, S013

S015 · implies

Before

target -2; all source rows examined

After

fiber=[-4, -3]; size=2

Conditions: none

List every preimage of this target;an unhit codomain element still has an empty fiber of size0.

Step identifiers and dependencies

Rule: complete_codomain_fiber · Uses: G001, S014

S016 · implies

Before

target -1; all source rows examined

After

fiber=[-6, -5]; size=2

Conditions: none

List every preimage of this target;an unhit codomain element still has an empty fiber of size0.

Step identifiers and dependencies

Rule: complete_codomain_fiber · Uses: G001, S015

S017 · implies

Before

[[-3, [-2, -1]], [-2, [-4, -3]], [-1, [-6, -5]]]

After

all fibers have size≤1: No

Conditions: none

Injectivity forbids distinct inputs with the same output,exactly the condition that every fiber has size at most1.It holds vacuously for an empty domain.

Step identifiers and dependencies

Rule: injectivity_fiber_test · Uses: G001, S016

S018 · implies

Before

missing codomain targets=[-8, -7, -6, -5]

After

all codomain fibers nonempty: No

Conditions: none

Surjectivity requires a preimage for every codomain element.The universal condition is true for an empty codomain,but the total-function premise is still required.

Step identifiers and dependencies

Rule: surjectivity_fiber_test · Uses: G001, S017

S019 · implies

Before

injective=No;surjective=No

After

requested result=No

Conditions: none

A bijection is both injective and surjective;the fiber profile is numerically ordered over the entire codomain,including zero fibers.

Step identifiers and dependencies

Rule: bijection_requested_classification · Uses: G001, S018

Reverse checks

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 — Check against the original data and this step's premises; a one-way implication is not an equivalence.
S017 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
S016 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
S015 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
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 — Check against the original data and this step's premises; a one-way implication is not an equivalence.
S012 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
S011 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
S010 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
S009 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
S008 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
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 — Check against the original data and this step's premises; a one-way implication is not an equivalence.
S005 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
S004 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
S003 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
S002 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.
S001 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.

Result

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: fa8108a79119abc95785d90afd3e0dee1598fb83e0d6e52c9c9d2be6d765a772
candidate record SHA-256: ab97ea7f592399759a41ed423e3e54a80e519d765c55b4cb0fca9a6a9f90bd2c
semantic review receipt SHA-256: 312ae86315346b8955842a547cb2d09246e1f826755f72c2a51f042e5c7d5c56
question-first witness SHA-256: 831f449ed41ff9144a290e534aa32adf7252d15b81c16ed5886a7dfd65dee70c
Lean: NOT_RUN · human review: NOT_PERFORMED

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