[1 -1 3 1 0 4] [1 0 4 0 1 0]
[1 0 4 -2 7 0] [0 1 1 0 -2 0]
Let A= [-1 -1 -5 3 -8 4] This matrix row reduces R=[0 0 0 1 -3 0]
[-2 3 -5 -1 -5 0] [0 0 0 0 0 1]
[4 -3 13 4 -2 3] [0 0 0 0 0 0]
Which variables (out of x₁,x₂,....,x₆) are free variables?