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

Answer 1

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.

Answer 2

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