Find all solutions to the following system of linear equations:

(x1) – 2(x2) – (x3)+(x4)=1

2(x1) – 3(x2) + (x3) – (x4)=6

3(x1) – 3(x2) + 6(x3))=15

(x1) + 5(x3)+(x4)=9

Using a system of linear equations, I found:

1 -2 -1 0 1

0 1 3 -3 4

0 0 0 6 0

0 0 0 0 0

so three solutions are:

(x1)=9, (x2)=4, (x3)=0, (x4)=0

(x1)=4, (x2)=1, (x3)=1, (x4)=0

(x1)=-1, (x2)=-2, (x3)=2, (x4)=0

How do I write my final solution (ie:what form)?