Gaussian elimination (pivoting)

In summary: The Attempt at a SolutionI don't think the lecturer is correct . Can someone explain about it ? I have read a lot of online resource , i can't find them similar to the way that the lecturer read [/B]Not clear to me what your question is. I see a piece of text in hhh.jpg and a worked out pivoting example in 140116.jpg and 140126Is 134955.jpg what you call 'the second photo' ? It only shows a swap of row 1 and 2 of a different matrix.What is it you think the lecturer does incorrectly ? placing the -3 in position 11 is according to the text.Not clear to me what your question is
  • #36
fonseh said:
Or the notes in this picture is misleading ? It mentioned that the a11 or a22 is 0 , not when we pivot the a11 , the a21 and a31 is 0 ...

The note you post is 100% clear, so you must be reading it incorrectly. Remember: after swapping rows 1 and ##i##, the old row ##i## becomes the new row 1, and vice-versa. The old ##a_{i1}## becomes the new ##a_{11}##, and the old ##a_{11}## becomes the new ##a_{i1}##.
 
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  • #37
Ray Vickson said:
The note you post is 100% clear, so you must be reading it incorrectly. Remember: after swapping rows 1 and ##i##, the old row ##i## becomes the new row 1, and vice-versa. The old ##a_{i1}## becomes the new ##a_{11}##, and the old ##a_{11}## becomes the new ##a_{i1}##.
It didnt mention about when after swapping row , the old a11 will become 0
 
  • #38
fonseh said:
It didnt mention about when after swapping row , the old a11 will become 0

No, you didn't, but the posted note DID, and that is all that counts here. You are trying to understand what the note is all about, and whether the note is correct. It is correct. (The note itself did not say that the old row i becomes the new row 1, etc., but it takes that as understood by the reader.)
 

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