Question 13820: Evaluate a Candidate Bilinear Form without Presuming an Inner Product

Original question and givens

Use the exact real R² candidate B(x,y)=x^T A y with the complete integer matrix A=[[21, 2], [2, 5]]. Bilinearity follows from the formula; symmetry and strict positive definiteness remain separate obligations. For a symmetric 2-by-2 matrix the Sylvester certificate requires a positive leading entry and positive determinant. Positive semidefiniteness or finitely many positive samples are insufficient, and completeness is not inferred. x=[2, 2], y=[3, -7]. Give (matrix,x,y,value). This evaluation family does not first require the symmetry and positive-definite checks to pass.

• G001 — Use the exact real R² candidate B(x,y)=x^T A y with the complete integer matrix A=[[21, 2], [2, 5]]. Bilinearity follows from the formula; symmetry and strict positive definiteness remain separate obligations. For a symmetric 2-by-2 matrix the Sylvester certificate requires a positive leading entry and positive determinant. Positive semidefiniteness or finitely many positive samples are insufficient, and completeness is not inferred. x=[2, 2], y=[3, -7]. Give (matrix,x,y,value). This evaluation family does not first require the symmetry and positive-definite checks to pass.

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-real-inner-product-space

Step-by-step derivation

candidate real R2 form;matrix=[[21, 2], [2, 5]];B(x,y)=x^T*A*y

matrix distributivity supplies bilinearity;other inner-product obligations remain separate

candidate evaluation matrix second slot:matrix=[[21, 2], [2, 5]];input=[3, -7]

input dimension=2;output dimension=2;rows dot input

candidate evaluation matrix second slot row0 column0 product := mul(21, 3)

candidate evaluation matrix second slot row0 column0 product = 63

candidate evaluation matrix second slot row0 column1 product := mul(2, -7)

candidate evaluation matrix second slot row0 column1 product = -14

candidate evaluation matrix second slot row0 sum := sum(63, -14)

candidate evaluation matrix second slot row0 sum = 49

candidate evaluation matrix second slot row1 column0 product := mul(2, 3)

candidate evaluation matrix second slot row1 column0 product = 6

candidate evaluation matrix second slot row1 column1 product := mul(5, -7)

candidate evaluation matrix second slot row1 column1 product = -35

candidate evaluation matrix second slot row1 sum := sum(6, -35)

candidate evaluation matrix second slot row1 sum = -29

candidate evaluation first coordinate0 product := mul(2, 49)

candidate evaluation first coordinate0 product = 98

candidate evaluation first coordinate1 product := mul(2, -29)

candidate evaluation first coordinate1 product = -58

candidate evaluation bilinear sum := sum(98, -58)

candidate evaluation bilinear sum = 40

Reverse checks

• S011 · premise_and_result_audit — Recompute candidate evaluation bilinear sum with exact rational arithmetic, not rounded decimals.
• S010 · premise_and_result_audit — Recompute candidate evaluation first coordinate1 product with exact rational arithmetic, not rounded decimals.
• S009 · premise_and_result_audit — Recompute candidate evaluation first coordinate0 product with exact rational arithmetic, not rounded decimals.
• S008 · premise_and_result_audit — Recompute candidate evaluation matrix second slot row1 sum with exact rational arithmetic, not rounded decimals.
• S007 · premise_and_result_audit — Recompute candidate evaluation matrix second slot row1 column1 product with exact rational arithmetic, not rounded decimals.
• S006 · premise_and_result_audit — Recompute candidate evaluation matrix second slot row1 column0 product with exact rational arithmetic, not rounded decimals.
• S005 · premise_and_result_audit — Recompute candidate evaluation matrix second slot row0 sum with exact rational arithmetic, not rounded decimals.
• S004 · premise_and_result_audit — Recompute candidate evaluation matrix second slot row0 column1 product with exact rational arithmetic, not rounded decimals.
• S003 · premise_and_result_audit — Recompute candidate evaluation matrix second slot row0 column0 product with exact rational arithmetic, not rounded decimals.
• 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

([[21, 2], [2, 5]], [2, 2], [3, -7], 40)

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.