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## Homework Statement

I feel like I should know the answer to this, so I believe this to be an easy question. Say have matrix A, and I store the elimination matrices E_1,1 E_2,1 etc. and somewhere in the elimination process I have to use a permutation matrix to swap rows. My question is when I find the the final elimination matrix in which I multiply together all elimination matrices I used to get down to reduce row echelon form, do I also multiply by the permutation matrix?

Example:

I have [A] and than I multiply by E_1,1.

Then I multiply by E_2,1

Then I multiply by P_4,3 and am now in reduce row ecehlon form

when I go to find E is it

E = P_4,3 * E_2,1 * E_1,1

or is it just

E = E_2,1 * E_1,1

Thanks for any help.