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Homework Help: Evaluating matrices

  1. Apr 27, 2006 #1
    hi there how would you go about evaluating a matrices? for example. evaluate A



    i need to know this for my homework? it sounds simple but my book does not cover this. Any help would be great.

    Kind Regards

  2. jcsd
  3. Apr 27, 2006 #2


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    `Evaluate' in what way?

    And is...

    [tex]A=\left(\begin{array}{c} -3 & 11 & 6 \end{array}\right)[/tex]
  4. Apr 27, 2006 #3


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    You don't "evaluate" a matrix, just as you don't evaluate a number! You can, of course, evaluate a matrix function just as you can evaluate a numerical function.

    [tex]f(x)= \left(\begin{array}{c} -3x \ x^2 & 4x^3 \ 6x \end{array}\right)[/tex]
    Then it would make sense to evaluate that matrix (function) at, say, x= 2.
  5. Apr 27, 2006 #4
    i see, what about Evaluate | u | does that make sense?
  6. Apr 27, 2006 #5


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    For a given value of u, yes. It makes sense to "evaluate" any formula in one or more variables for given values of those variables. "Evaluate" means to determine the value of a formula when replacing the variables by numbers.
  7. Apr 27, 2006 #6


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    Is your "u" a square matrix? If so, then "Evaluate |u|" might mean "Compute the determinant of the square matrix u". In the context of HallsofIvy's post, the "formula" is the rule to compute the determinant of a square matrix and the "variable" is the square matrix u.
  8. Apr 28, 2006 #7


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    Yeah - that makes sense.

    For [tex]u=(-3, 11, 6)[/tex]

    The magnitude [tex]|u|=\sqrt{(-3)^2+11^2+6^2}[/tex]
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