Hi again, I'm not sure if it's okay for me to post in here again, as I posted last night--but this is truly urgent. I'll be taking a midterm in a short while and there are several questions on my study guide that have me completely stumped:

1. y + z = 2

x + y + z = -1

-x + z = -1

I have done this problem again and again, only to end up with different/wrong answers for x, y, and z each time. I know that I have to created an augmented matrix, so I did that, and then I continued to row reduce until I got the identity matrix on my left, and the the supposed (yet incorrect) solutions on the right. I don't know what I'm doing wrong here, and I'm beyond frustrated.

2. 2y + z = 0

y + z = 1

x - y = -1

Same situation here. I created the augmented matrix and then, when I saw that column one is [0 0 1], I don't know what to do.

3. -x + y +2z = 1

2x -2z = 0

2x + y + 2z = 0

I switched the first and second row here, then divided the first row by 2, and proceeded to use G-J, but messed up my calculations because I'm not getting the correct solutions for x, y, and z...I've re-done over and over and I'm not sure what I'm doing incorrectly.

4. 2x + y - z = 0

-x + y = 1

2x + y + 2z = 0

Same situation here...I've done the problem repeatedly only to end up with different x, y and z each time.

5. Suppose a two by two matrix A is nonsingular and is defined as follows:

A = ( a b

0 d ) < The whole thing is supposed to be in the parenthesis

where a, b, d are real numbers. Use Gauss-Jordan to find the inverse of A.

Again...I am at a total loss here. I think that I have to put an identity matrix in there somewhere?

I'd really appreciate the help on this...I have no idea what I'm doing, and I'm definitely panicking. THANK YOU!