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This question already has an answer here:

Please help me complete my answer and find the matrix associated to a given quadratic form, here is my work and effort on that

(https://i.stack.imgur.com/TF8eb.jpg)

Here's my attempt to answer it

(https://i.stack.imgur.com/dFfaN.jpg)

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marked as duplicate by amd, Lord Shark the Unknown, Xander Henderson, José Carlos Santos, Namaste Oct 19 '18 at 9:57

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

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

Recall that for a skew symmetric matrix $S$

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

and that

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

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  • $\begingroup$ 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'? $\endgroup$ – A.D.P Oct 18 '18 at 14:18
  • $\begingroup$ @A.D.P Do you know what is a skew symmetric matrix? Refer to LINK $\endgroup$ – gimusi Oct 18 '18 at 14:21
  • $\begingroup$ Is it when matrix A' = -A? $\endgroup$ – A.D.P Oct 18 '18 at 14:23
  • $\begingroup$ @A.D.P Yes exactly! $\endgroup$ – gimusi Oct 18 '18 at 14:24
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    $\begingroup$ okay got it. Thank you so much for your respond :) $\endgroup$ – A.D.P Oct 18 '18 at 14:26

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