1 1 -1 0
2 1 -2 1
3 0 -4 1
-2R1 + R2
R2
1 1 -1 0
0 -1 0 1
3 0 -4 1
-3R1 + R3
R3
1 1 -1 0
0 -1 0 1
0 -3 -1 1
-R2
R2
1 1 -1 0
0 1 0 -1
0 -3 -1 1
3R2 + R3
R3
1 1 -1 0
0 1 0 -1
0 0 -1 -2
-R3
R3
1 1 -1 0
0 1 0 -1
0 0 1 2
-R2 + R1
R1
1 0 -1 1
0 1 0 -1
0 0 1 2
R3 + R1
R1
1 0 0 3
0 1 0 -1
0 0 1 2
By the way, your plea to "please help me as soon as possible" is either a null request or unsufferable arrogance. If you are being helped, then by definition you are being helped as soon as possible -- it simply depends on who gets to decide how soon possible is. That would be the volunteer tutors, by the way. On the other hand, if by "please help me as soon as possible" actually means, "hey you, drop whatever you are doing even if it is helping someone else and pay attention to MY problem" then it is not only unsufferable but unconsionable arrogance on your part.
John

My calculator said it, I believe it, that settles it