Problem????

Discussion in 'Math' started by dogar sahab, Oct 29, 2008.

  1. dogar sahab

    Thread Starter Active Member

    Mar 15, 2008
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    Q-If the product AB is the zero matrix,AB=0 show that the coulumn space of B is contained in the nullspace of A???
    HOW??>>
     
  2. Mark44

    Well-Known Member

    Nov 26, 2007
    626
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    Do you know what the terms column space and nullspace mean? If you find these for me I'll help you out.
     
  3. dogar sahab

    Thread Starter Active Member

    Mar 15, 2008
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    I know how to find but this is an abstract question...so its a proof and i am not getting how to do it!!!
    I know null space is
    Ax=0
     
  4. Dave

    Retired Moderator

    Nov 17, 2003
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  5. Mark44

    Well-Known Member

    Nov 26, 2007
    626
    1
  6. Mark44

    Well-Known Member

    Nov 26, 2007
    626
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    This is not the definition of the null space. If you don't know what the null space and column space mean, you won't be able to do the proof. I guarantee it.
     
  7. Dave

    Retired Moderator

    Nov 17, 2003
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    Sorry, I just thought you were up for a challenge! :D

    Agreed.

    Dave
     
  8. dogar sahab

    Thread Starter Active Member

    Mar 15, 2008
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    I didnt want to get into details of definition..
    If u want then
    Column space of any matrix is actually the space spanned by the independent coulums of the given matrix!!!The all other colmn are just the linear combinations of the the columns that lie in the column space...So the whole column space generated by the independent columns of a matrix..This is what the basic concept of column space!!!!
     
  9. Mark44

    Well-Known Member

    Nov 26, 2007
    626
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    That's roughly it- the column space of a matrix is the space spanned by its columns (you don't need to add "independent").

    Now, what is the nullspace of a matrix A?

    Your earlier answer
    doesn't convince me that you know what the term null space means.
     
  10. dogar sahab

    Thread Starter Active Member

    Mar 15, 2008
    116
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    I guess the term INDEPENDENT COULUMS is more accurate because the dependent columns are included in that space as the dependent columns are actually linear combinations of independent columns!!!
     
  11. Mark44

    Well-Known Member

    Nov 26, 2007
    626
    1
    The column space is the space spanned by the columns of a matrix, whether the columns are independent or dependent vectors. If the columns are linearly independent, the the dimension of the space is the same as the number of columns, and the columns will form a basis for the space. If the the columns are linearly dependent, then the dimension of the space will be less than the number of columns.

    Did you ever come up with the definition for the nullspace of a matrix?
     
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