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Math Help - Finding a vector

  1. #1
    Senior Member Mukilab's Avatar
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    Finding a vector

    P is the point 2,3
    Q is the point 6,6

    Write down vector PQ in column form. I got 4 over 3 (not sure how to use latex with this one)

    The question:

    PQRS is a prallelogram
    Vector PR (not sure how to make the vector sign in latex) = 4 over 7
    Find vector QS

    I did -4 over -4 + 0 over 4 and got -4 over 1 as an answer.

    Correct?
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  2. #2
    Senior Member Mukilab's Avatar
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    Anyone?
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  3. #3
    MHF Contributor
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    Hi

    Your answer is correct but I haven't understood how you got it

    \vec{PR} = \binom{4}{7}

    \vec{PQ} = \binom{4}{3}

    \vec{QS} = \vec{QP} + \vec{PR} + \vec{RS} = 2 \vec{QP} + \vec{RS} = \binom{2 \times (-4) + 4}{2 \times (-3) + 7} = \binom{-4}{1}
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  4. #4
    Senior Member Mukilab's Avatar
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    \vec{QR}=\vec{PS}
    \vec{PQ}=\vec{SR}=\binom{4}{3}


    Because  \vec{PR}=\binom{4}{7}
    \vec{QR}=\binom{0}{4}=\vec{PS}

    Because  \vec{QS}=\vec{-PQ}+\vec{PS}
    \vec{QS}=\binom{-4}{-3}+\binom{0}{4}=\binom{-4}{1}
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  5. #5
    MHF Contributor
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    Well done
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  6. #6
    Senior Member Mukilab's Avatar
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    thanks
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