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Math Help - very easy but im stuck plz help me

  1. #1
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    very easy but im stuck plz help me

    hi every one im new member in this fourm ..and i need your help...

    this is the question

    Suppose , and .
    Compute the following values

    ||2u-4v+w||=

    how to compute this????
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  2. #2
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    Quote Originally Posted by falta View Post
    hi every one im new member in this fourm ..and i need your help...

    this is the question

    Suppose , and .
    Compute the following values

    ||2u-4v+w||=

    how to compute this????
    I assume that you are trying to find |2\mathbf{u} - 4\mathbf{v} + \mathbf{w}|.


    2\mathbf{u} - 4\mathbf{v} + \mathbf{w} = 2(3\mathbf{i} + \mathbf{j} + 5\mathbf{k}) - 4(5\mathbf{i} - 3\mathbf{j} + 3\mathbf{k}) + (-4\mathbf{i} - 4\mathbf{j} - 3\mathbf{k})

     = 6\mathbf{i} +2\mathbf{j} + 10\mathbf{k} - 20\mathbf{i} + 12\mathbf{j} - 12\mathbf{k} -4\mathbf{i} - 4\mathbf{j} - 3\mathbf{k}

     = -18\mathbf{i} + 10\mathbf{j} - 5\mathbf{k}.


    So |2\mathbf{u} - 4\mathbf{v} + \mathbf{w}| = \sqrt{(-18)^2 + 10^2 + (-5)^2}

     = \sqrt{324 + 100 + 25}

     = \sqrt{449}
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  3. #3
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    thank u very much i got 10 on 10 because of u ....thanx
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