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Homework Help: Problem involving the adjugate

  1. Aug 10, 2007 #1
    The question I'm dealing with is this:

    Suppose adj(A) =
    -1 2 -4
    0 -3 0
    0 0 3
    Find A

    I was trying to figure it out backwards, by using a 3x3 matrix of variables and doing the cofactor expansion thing and then seeing if I could figure out the values of the variables, but I'm not sure that's the way to go. I suspect there is a formula or theorem out there that will help me, but I can't figure out what it is.

    Any help?
  2. jcsd
  3. Aug 11, 2007 #2
    Is the determinant of A given?
    If it is so you can use A*adj(A)=det(A) *identity matrix
    But if it is not i don't know what to do
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