Is the solution to problem 4.2 in the check yourself section correct. Instead of all 1's in the lower diagonal it seems that it should be all -1's in the lower diagonal.

Thanks, Nate

Question

Is the solution to problem 4.2 in the check yourself section correct.  Instead of all 1's in the lower diagonal it seems that it should be all -1's in the lower diagonal.

Thanks, Nate

anonymous · Answer

Hi Nate, 
The elimination matrices do contain the number -1. However, we are using the inverse of the elimination matrices to find the matrix U, hence the number 1 would appear instead of -1. If you multiply L and U you'll find that it indeed produces A.

anonymous · Answer

You're correct and I see my mistake.  Thank you.