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desalexus

  • one year ago

How can you determine whether a matrix product AB is defined?

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  1. Loser66
    • one year ago
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    @Mertsj explain him, please.

  2. Mertsj
    • one year ago
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    You're doing fine. Give an example. That will help.

  3. desalexus
    • one year ago
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    its HER and like this A is 2×3 and B is 3×2, so AB is (2×3)(3×2).

  4. RolyPoly
    • one year ago
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    \[A_{m\times n}B_{n\times p}\]? The number of columns of A = number of rows of B

  5. RolyPoly
    • one year ago
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    Dimension of AB would be m×p

  6. desalexus
    • one year ago
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    Thanks

  7. Mertsj
    • one year ago
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    It depends on the dimensions:

  8. mathmale
    • one year ago
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    The example that Desalexus presents is illustrative: A is 2×3 and B is 3×2, so AB is (2×3)(3×2). Note how Matrix A has 2 rows and 3 columns, and B 3 rows and 2 columns. We can indeed multiply matrices A and B (in that order).

  9. Mertsj
    • one year ago
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    |dw:1388979444164:dw|

  10. Mertsj
    • one year ago
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    |dw:1388979475429:dw|

  11. RolyPoly
    • one year ago
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    |dw:1388979474597:dw|

  12. mathmale
    • one year ago
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    Yes, Mertsj, and you can make that statement more precise by stating that "the number of columns of the first matrix must equal the number of rows of the second. RolyPoly is correct in his drawing (immediately above), whereas I found that I was wrong at the onset (and have deleted my incorrect statement accordingly)!

  13. mathmale
    • one year ago
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    I'd rather find my own mistakes than have someone else find them for me! :)

  14. Mertsj
    • one year ago
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    Sometimes it is easier for the asker to see an example than to decipher a bunch or words but it is good to have both so the asker can choose.

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