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Basic linear algebra help. Converting equation to matrix form

  1. Sep 29, 2010 #1
    1. The problem statement, all variables and given/known data
    Express the equation [tex]q=x_1 - 6x_2 + 3x_1^2 + 5x_1 x_2[/tex] in the matrix form [tex]1/2x^T Q*x+c^T x[/tex]

    2. Relevant equations
    The only mention of a matrix c that I could find in my book is in the section of Gaussian elimination:

    [tex]c= \frac {a_{ik}}{a_{kk}}[/tex]

    But I don't feel like this has anything to do with the solution form I'm trying to find.

    3. The attempt at a solution
    I'm not sure where to begin really. I feel like this should be a very simple problem, but I'm not sure where to start. I tried defining x = [x1 x2] and Q = [q1 q2] but I'm not sure what the "c" matrix is supposed to be.

    As some background, this is taken from the review portion of my Finite Elements book.
    Last edited: Sep 29, 2010
  2. jcsd
  3. Sep 29, 2010 #2


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    Homework Helper

    Q will be a 2x2 matrix, while c will be a 2x1 column vector - they have to be of that form to match the multiplication and as q is a scalar
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