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Math Help - vector mutiplication.

  1. #1
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    Post vector mutiplication.

    u=2i+j, v= i+j, and w= i-j. u = av +bw where a and b are scalars. find a and b.

    I have tried a buttload of numbers and none seem to work because one when I add them together to form u one is negative and there is no negative in u.
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  2. #2
    Rhymes with Orange Chris L T521's Avatar
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    Quote Originally Posted by hotdogking View Post
    u=2i+j, v= i+j, and w= i-j. u = av +bw where a and b are scalars. find a and b.

    I have tried a buttload of numbers and none seem to work because one when I add them together to form u one is negative and there is no negative in u.
    Note that x\mathbf{i}+y\mathbf{j}=\left<x,y\right> (just thought I would mention that, just in case my notation confused you).

    Plug the vectors into the equation to get

    \left<2,1\right>=a\left<1,1\right>+b\left<1,-1\right>\implies \left<2,1\right>=\left<a+b,a-b\right>

    Therefore, a+b=2 and a-b=1.

    Can you solve these for a and b?
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