This is the question i am trying to solve...

http://img151.imageshack.us/img151/7596/mathprob.jpg

U is a 3x3 matrix.

However, when i put my answer in I get only part marks... 78% right.

My attempt:

I found that to get B, I had to use elementary row operations. Mine were:

-2r1 + r2 --> r2

and r1 + r3 --> r3

after that I used an identity to find U, and i applied the same row operations.

My matrix/U looked like this after:

1 0 0

-2 1 0

1 0 1

What am i doing wrong???

UPDATE:

I just figured it out...

I just had to invert U to get my answer