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Vectors with uknowns problem

  1. Jun 4, 2009 #1
    1. The problem statement, all variables and given/known data
    If A= (5.00 -7.00 ) units, B= (-7.00 + 2.00 ) units, and C= (27.0 + 20.0 ) units, determine a and b such that aA+ bB + C = 0.


    2. Relevant equations
    What I did to try and figure this out was solve for a and got the result of
    a = -bB - C/ A

    3. The attempt at a solution

    What I did to try and solve this equation was plug that in for a, and take all the magnitudes of the vectors that are stated above but when i proceeded to do that everything would just cancel out when attempting to solve for b at that point. Any help would be great thank you.
     
  2. jcsd
  3. Jun 4, 2009 #2

    Cyosis

    User Avatar
    Homework Helper

    You can't divide vectors like that. Secondly i take it that A=(5.00 , -7.00) is what you meant right? The way you have written it now suggests A=-2.

    Plugging the components of the vectors into the vector equation will give you two "normal" equations. Since you have two unknowns and two equations you can solve a and b.

    [tex]
    \begin{align}
    &5a-7b+27=0
    \\
    &-7a+2b+20=0
    \end{align}
    [/tex]
     
  4. Jun 4, 2009 #3
    yes it was A = (5i, -7j), and thank you very much for the help.
     
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