C1W2 Gaussian Elimination Algorithm - Where did -1 come from?

Maybe I’m not following correctly but where did the -1 in row 2 come from? The original row 2 from where the instructor copied the row from does not have a -1 in the 4th column. It’s confusing me a lot.

Thanks for any help

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Hi @zero26!

Thank you for pointing this out. You are correct. There is actually an inconsistency in the slide. If you notice in the slide around 5:20, the value of the last column in second row is -1, but when the slide changes, it is changed to 0 - an error indeed. However, the error is not propagated to the row operation below the matrix as you pointed. I will forward it to our video team to fix the slide.

Thanks,
Lucas

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Yes indeed. I actually went back, took a pen and solved it myself using the video as a guide. That cleared up my confusion.

Thanks a lot!

Has anyone pointed out this error before me? I actually searched the forums for this same issue before making a new topic as a couldn’t find anything.