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Reduced row echelon form question

  1. Jun 24, 2010 #1
    My book gives the following definition for reduced row echelon form:

    1) If a row has nonzero entries, then the first nonzero entry is 1, called the leading 1 in this row.
    2) If a column contains a leading 1, then all other entries in that column are zero.
    3) If a row contains a leading 1, then each row above contains a leading 1 further to the left.

    1 and 3 I understand, but 2 I don't fully understand - does that mean a 'column leading 1', as in if I start at the top of a column and go down the numbers then the first nonzero entry is a 1, or does it mean that if a column contains a 1 that is a leading 1 for its row?

    Thanks!
     
  2. jcsd
  3. Jun 24, 2010 #2

    Landau

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    Science Advisor

    No, it means a "row leading 1", as defined in 1). So, if a ROW has a leading 1, than in the COLUMN of that particular leading 1 all other entries are zero. Perhaps the wkikipedia definition is clearer.
     
  4. Jun 24, 2010 #3
    Thank you!
     
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