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Math Help - Vector..

  1. #1
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    Vector..

    Given that a=3i-2j, b=3i+j and c=-6i+j, express pa-qb in terms of p,q,i and j. Hence, find the value of p and of q if pa-qb is equal to the unit vector along the straight line 4x+3y=12
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  2. #2
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    Re: Vector..

    Quote Originally Posted by Trefoil2727 View Post
    Given that a=3i-2j, b=3i+j and c=-6i+j, express pa-qb in terms of p,q,i and j. Hence, find the value of p and of q if pa-qb is equal to the unit vector along the straight line 4x+3y=12
    Do you intend to show any of your own work?
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  3. #3
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    Re: Vector..

    well, I have to admit that I don't know how to solve it..
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  4. #4
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    Re: Vector..

    Trefoil it is simple...
    what pa means?
    what qb means?

    multiplicationnnnn..........so as Plato suggests........ just do itttttttttttttttttttttt .

    then we can help you for the last part...
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  5. #5
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    Re: Vector..

    You are told exactly what to do: you are given pa+ qb and you are told that a= 3i-2j, b=3i+j. It's just integer arithmetic.
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    Re: Vector..

    this interesting



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    Re: Vector..

    Really good one question and i don't solve this question and if you know the answer just share with me.
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  8. #8
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    Re: Vector..

    Given that a=3i-2j, b=3i+j and c=-6i+j, express pa-qb in terms of p,q,i and j. Hence, find the value of p and of q if pa-qb is equal to the unit vector along the straight line 4x+3y=12
    Since it has been a while: It is, as I said, integer arithmetic. pa= p(3i- 2j)= 3pi- 2pj. qb= q(3i+ j)= 3qi+ qj. pa- qb= 3pi- 2pj- (3qi+ qj)= (3p- 3q)i-(2p+ q)j.

    A vector pointing along the straight line 4x+ 3y= 12 is 4i+ 3j which has length \sqrt{4^2+ 3^2}= 5 so a unit vector in that direction is (4/5)i+ (3/5)j

    We have (3p- 3q)i- (2p+ q)j= (4/5)i+ (3/5)j so solve 3p- 3q= 4/5 and -2p- q= 3/5 for p and q.
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