I just had a question on my final and i dont remember ever hearing of it(and judging by the fact that 2/3 my class was asking about it im not the only one)

We where required to show the elementary matrix corresponding to each elementary row operation we performed while reducing a matrix ro rref.

for instance what would the elementary matrix be for

| 1 3 | = | 1 3 |

| 3 1 | = | 0 -8| (r2+-3r1)