# Find the matrix that associated to a given quadratic form [duplicate]

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Please help me complete my answer and find the matrix associated to a given quadratic form, here is my work and effort on that Here's my attempt to answer it ## marked as duplicate by amd, Lord Shark the Unknown, Xander Henderson, José Carlos Santos, NamasteOct 19 '18 at 9:57

• Again, it would be great if you'd make some effort to write down you work using MathJax. – gimusi Oct 18 '18 at 14:08

HINT

Recall that for a skew symmetric matrix $$S$$

$$v^TSv=0 \quad \forall x$$

and that

$$v^T(A+S)v= v^TAv+v^TSv$$

• Thank you for answering my question, but i'm sorry i still don't understand what matrix A and S standing for, are those equal to matrix A and B or B and B'? – A.D.P Oct 18 '18 at 14:18
• @A.D.P Do you know what is a skew symmetric matrix? Refer to LINK – gimusi Oct 18 '18 at 14:21
• Is it when matrix A' = -A? – A.D.P Oct 18 '18 at 14:23
• @A.D.P Yes exactly! – gimusi Oct 18 '18 at 14:24
• okay got it. Thank you so much for your respond :) – A.D.P Oct 18 '18 at 14:26