Question

solve using the gauss-jordan method.
x-2y+4z=7
-x+3y-z=-1
2x+y=-2

*I get through the first two columbs, but can't get the third one to the one and zero.

Answer 1

http://www.irs.gov/pub/irs-pdf/i1040tt.pdf

Step 2: Enter the values for your matrix, and press the "Solve" button.
three rows, four columns
Input
+1 -2 +4 +7
-1 +3 -1 -1
+2 +1 +0 -2





Add (1 * row1) to row2
1 -2 4 7
0 1 3 6
2 1 0 -2

Add (-2 * row1) to row3
1 -2 4 7
0 1 3 6
0 5 -8 -16

Add (-5 * row2) to row3
1 -2 4 7
0 1 3 6
0 0 -23 -46

Divide row3 by -23
1 -2 4 7
0 1 3 6
0 0 1 2

Add (-3 * row3) to row2
1 -2 4 7
0 1 0 0
0 0 1 2

Add (-4 * row3) to row1
1 -2 0 -1
0 1 0 0
0 0 1 2

Add (2 * row2) to row1
1 0 0 -1
0 1 0 0
0 0 1 2

Answer 2

http://www.gregthatcher.com/Mathematics/GaussJordan.aspx

Answer 3

thanks, wasn't too sure whether I could divide by -23 or not. Found the website, was really helpfull =)