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Math Help - Matrix multiplication doubt

  1. #1
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    Matrix multiplication doubt

    I have to do a matrices operation given as A.X=B where A is an 1X1 matrix, x is a 3X1 matrix and B is a 3X3 matrix with elements of 3rd column zero. here A is unknown term and i wish to find the value of A. please guide me on how to solve this problem?
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  2. #2
    Junior Member alane1994's Avatar
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    Re: Matrix multiplication doubt

    Are there any numbers with this? Or is this all purely hypothetical/theoretical?
    Anywho... what you would do is you would take the B matrix, and then multiply it by the inverse of the X matrix to solve for A matrix. Seeing as it is sort a complicated process and rather awkward to put into words, I have a link that takes you to a great website that explains it better.
    Matrix Inversion: Finding the Inverse of a Matrix
    It is really a rather easy process. If you have questions, feel free to ask. I can break it down step by step if you wish.
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  3. #3
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    Re: Matrix multiplication doubt

    Hello, rcty!

    Are you sure you have typed the problem correctly?


    \text{I have to do a matrix operation: }\:A\cdot X\:=\:B
    \text{where }A\text{ is a }1\!\times\!1\text{ matrix, }X\text{ is a }3\!\times\!1\text{ matrix,}
    \text{and }B\text{ is a }3\!\times\!3\text{ matrix with elements of 3rd column zero..}

    \text{I wish to find the value of }A.

    Do you realize what you are asking?

    \text{The equation is: }\:\begin{bmatrix}a\end{bmatrix}\cdot \begin{bmatrix}x_1 \\ x_2 \\ x_3 \end{bmatrix} \;=\; \begin{bmatrix}b_1&b_2&0 \\ b_3 &b_4 & 0 \\ b_5&b_6&0 \end{bmatrix}


    First of all, you cannot multiply a [1\!\times\!1] by a [3\!\times\!1]

    Even if you could, you wouldn't get a [3\!\times\!3].
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