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Homework Help: Addition of undefined matrices

  1. Mar 24, 2012 #1
    1. The problem statement, all variables and given/known data


    D=3row x 3col
    C=2row X 3col
    A=3row X 2col

    3. The attempt at a solution

    It is my understanding that a row of a matrix is horizontal variables and a column is the vertical variables. And for multiplication of two matrices you need the colums of the first matrix to be equal to the number of rows in the second matrix.

    so DB= (D3x3)x(A2x2) so therefore DB is undefined.

    The transpose of A3x2->A2x3 so CA^T = (C2x3) x (A2x3) Which is also undefined.

    So does this then mean that the answer for DB+CA^T-2A is just undefined or is the answer -2A? I am unsure what the answer is or how to word it correctly
  2. jcsd
  3. Mar 24, 2012 #2


    User Avatar

    Staff: Mentor

    Yes, those elements.
    I'd say undefined.
  4. Mar 24, 2012 #3
    Excellent thankyou, sorry if this was in the wrong area, I prob should of put it in math not eng.
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