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Homework Help: Integer eigenvalues problem

  1. Sep 15, 2007 #1
    1. The problem statement, all variables and given/known data
    I need the eigenvalues of [[3, -1][-1, 1]] (ie [[row1][row2]])

    3. The attempt at a solution

    A-xI = [[3-x, -1][-1, 1-x]]

    so I get the characteristic polynomial x^2-4x+2=0 from det(A-xI)=0

    Is this correct? Because I won't get integer eigenvalues from it
    Last edited: Sep 15, 2007
  2. jcsd
  3. Sep 15, 2007 #2
    Yeah, it is right.
  4. Sep 16, 2007 #3
    Won't that be really messy to bring the matrix A-xI to RREF? (with x non-integer)
  5. Sep 16, 2007 #4
    But in general, there is no reason why things have to be integer...
  6. Sep 16, 2007 #5
    Last edited: Sep 16, 2007
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