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How to determine what vector A is equal to?

  1. Apr 30, 2016 #1
    1. The problem statement, all variables and given/known data
    Three vectors are related as by the equations: A+B = 2C and B-2A = -C.
    If C= 1i + 2j +3k then what is vector A equal to?

    2. Relevant equations
    i, j, and k are unit vectors


    3. The attempt at a solution
    The solution in my answer key says that vector A = vector C but I don't understand how they arrived at that. Any clarification would be appreciated, thanks!
     
  2. jcsd
  3. Apr 30, 2016 #2

    BvU

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    Hi eng, :welcome:

    A bit awkward if the template asks for relevant eqations, right ? You still need something there. The statement that ##\hat\imath, \hat \jmath, \hat k## are unit vectors is nice to form an idea, but it doesn't help solve the equations....

    If A, B and C were numbers, how would you solve A+B = 2C & B-2A = -C ?
     
  4. Apr 30, 2016 #3
    Hi! Thanks for taking a look at my question and if they were numbers would I combine the 2 equations? A's and B's on one side with C's on the other and get A-2A + B+B = 2C-C (simplified: -A +2B = C)?
     
  5. Apr 30, 2016 #4

    haruspex

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    You are looking for a relationship between A and C. So you need to combine the equations in a way which .... does what?
     
  6. Apr 30, 2016 #5
    something that eliminates the B from the equation? Subtract them?
     
  7. Apr 30, 2016 #6

    haruspex

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    Of course.
     
  8. Apr 30, 2016 #7
    ohhh thanks I got it!
     
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