[ 1 1 1 |-1]
[-1 2 1 | 6]
[ 2 -1 3 |15]
R1 + R2→R2 means to add row 1 and row 2 and take what you get and
replace row 2 with it.
So we add row 1 and row 2
R1 = [ 1 1 1 |-1]
+ R2 = [ -1 2 1 | 6]
--------------------
R1+R2 = [ 0 3 2 | 5]
Now we replace row 2 with that sum:
[1 1 1 |-1]
[0 3 2 | 5]
[2 -1 3 |15]
-2R1+R3→R3 means to multiply R1 by -2 and add it to row 3
and take what you get and replace row 3 by it:
So we multiply row 1 by -2
R1 = [ 1 1 1 |-1]
×(-2)
-------------------
-2R1 = [ -2 -2 -2 | 2]
add to row 3--> R3 = [ 2 -1 3 |15]
--------------------
-2R+R3 = [ 0 -3 1 |17]
Now we replace row 3 by that result:
[1 1 1 |-1]
[0 3 2 | 5]
[0 -3 1 |17]
Edwin
