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Homework Help: Finding eigenvalues with the power series method

  1. Nov 7, 2009 #1
    1. The problem statement, all variables and given/known data
    Consider the matrix [1,-5,5;-3,-1,3;1,-2,2]
    Do four interations of the power method, beginning at [1,1,1] to approximate the dominant eigenvalues of A

    2. Relevant equations
    Matrix multiplication

    3. The attempt at a solution

    Okay my issue with this problem is this
    I set V0 = [1;1;1],
    Now I go to calculate u1
    u1 = A*V0 = [1,-5,5;-3,-1,3;1,-2,2]*[1;1;1]=[1;-1;1], V1 = u1 / (?) and what value should i divide it by, which one has the largest magnitude, would it be -1, because I know that is unique, otherwise, is it 1?
    Because ive tried both ways and im not sure which way to go on this.
  2. jcsd
  3. Nov 10, 2009 #2


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    Staff Emeritus
    Science Advisor
    Homework Helper

    You divide by the magnitude (i.e. length) of u1, or |u1|.
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