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Homework Help: Parameter of a determinant

  1. Dec 7, 2009 #1
    1. The problem statement, all variables and given/known data
    Hello all,

    I have a parameter x of a matrix M = [21, 7
    14, 7]
    the determinant of
    |(M - xI)| = 0

    2. Relevant equations

    I is known as the identity matrix

    3. The attempt at a solution
    My solution seems to be a bit far fetched:

    (21 - x)(7-x) - 98 = 0

    x2 - 28x + 147 - 98 = 0

    x2 - 28x + 49 = 0

    using the quadratic formula x = (28 +- root(28x28 - 4(1)(49))) / 2
    which I got to be 14 +- 7root(3)

    Is this the correct method and answer?

    Regards,
    Mr Lard
     
  2. jcsd
  3. Dec 7, 2009 #2

    Mark44

    Staff: Mentor

    Yes. And what you are calling parameters are usually called eigenvalues of the matrix.
     
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