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Math Help - Multiplying matrices what is W?

  1. #1
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    Multiplying matrices what is W?

    What is W in BWS = 3, where B = [4 9 -3 9] and S = [2 5 -1 0]. Note that S matrix is written vertically but I can't write it here.

    Is it not possible because B would have to be vertical to multiply with B, but then S is vertical and you can't multiply that with a vertical W? Or am I totally confused?
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  2. #2
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    Quote Originally Posted by brumby_3 View Post
    What is W in BWS = 3, where B = [4 9 -3 9] and S = [2 5 -1 0]. Note that S matrix is written vertically but I can't write it here.

    Is it not possible because B would have to be vertical to multiply with B, but then S is vertical and you can't multiply that with a vertical W? Or am I totally confused?
    thanks Soroban , time to revise my matrix
    Last edited by mathaddict; April 10th 2010 at 11:06 PM.
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  3. #3
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    So I got 56 for BS. I can't figure out W though.
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  4. #4
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    Hello, brumby_31

    Marix multiplication is not commutative!
    . . You cannot multiply out-of-order.



    What is W in BWS = 3,

    where B \:=\:\begin{bmatrix}4 & 9 & \text{-}3& 9\end{bmatrix}\,\text{ and }\,S \:=\:\begin{bmatrix}2\\5\\\text{-}1\\0\end{bmatrix}

    B\text{ is }1\times 4,\,\text{ and }\,S\text{ is }4\times 1 \quad\rightarrow\quad W\text{ is }4\times 4.


    The equaton has this form: . \begin{bmatrix}4&9&\text{-}3&9\end{bmatrix}\,\begin{bmatrix}a&b&c&d \\ e&f&g&h \\ i&j&k&l \\ m&n&p&q\end{bmatrix}\,\begin{bmatrix}2\\5\\\text  {-}1\\0\end{bmatrix} \;=\;\begin{bmatrix}3\end{bmatrix}


    We have 16 unknowns and (basically) one equation.

    Good luck!

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