is this an elementary matrix?

1 0
-5 1
if it is can you explain why?

Question

is this an elementary matrix?

1  0
-5  1
if it is can you explain why?

anonymous · Answer

huh where the answer went lol

akshay_budhkar · Answer

OMG joe u awake???

anonymous · Answer

what do you mean

anonymous · Answer

...no.... >.< yeah, i was lying in bed, but couldnt fall asleep.

anonymous · Answer

like times the first row by 5 then add it to the second row?

anonymous · Answer

Sorry let me rewrite this, one second.

anonymous · Answer

what if it is    -5    1
                       1     0

anonymous · Answer

http://en.wikipedia.org/wiki/Elementary_matrix#Row-addition_transformations

anonymous · Answer

the book says that won't be an elementary matrix but why

anonymous · Answer

An elementary matrix is the identity matrix modified by one single row operation

anonymous · Answer

Do you see why the second matrix is not?

anonymous · Answer

You need more than one row operation, you need a swap and a row addition.

anonymous · Answer

So it is the composition of two elementary row operations (elementary matrices)

anonymous · Answer

So anyways, the answer to the original question is yes.
It is the row addition operation (it is an elementary row operation matrix).

It scales the first row by -5 and adds it to the second.