Hi guys,

I've been given a question that asks me to use Gaussian elimination to reduce the following system of equation to row echelon form, hence solving for x, y, z and w

x+2y+z+w=1

2x+y-z-w=2

x+2y-3z+w=-3

x-y+z-w=3

I'm not really too comfortable with Gaussian elimination but so far I've managed to put it into matrix form and I've managed to get zeros in every place they need to be bar one:

|1 2 1 1| 1 |

|0 -3 -3 -3| 0 |

|0 0 -4 0| -4|

|0 -3 0 -2| 2 |

But I don't know how to continue on with my 4th row because the -3 is where it's meant to be zero.

I'm just super confused and any help would be appreciated!

Also sorry my matrix is dodgey, I don't know how to post it correctly!