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Homework Help: Block Multiplication

  1. Feb 12, 2007 #1
    Can someone explain "block multiplication" to me? It's not in the book, except in the context of a question as follows:

    So the rule is that Matrix [A B] * colum matrix [C D] = [AC+BD] And I am supposed to verify it. but can I just ask how I would go about doing that since I really don't know what block multiplication does or what I'm supposed to multiply? Thanks.
  2. jcsd
  3. Feb 12, 2007 #2


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    "Block multiplication" means that in your example A B C and D are matrices, not scalars. The dimensions of A B C and D must be compatible with each other, so the matrix expression AC + BD is defined. The row dimension of A is the same as the column dimension of C, etc.

    Verify it by showing it gives the same answer as the standard definition of matrix multiplication. Write A as an array of scalars [itex]a_{ij}[/itex] and so on.
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