X = (x1 x2)
(x3 x4)
3x1 + 5x2 = -1
-2x1 - 4x2 = 2
3x3 + 5x4 = -5
-2x3 - 4x4 = 6
=>
x1 + x2 = 1 => x1 = 1 - x2
x3 + x4 = 1 => x3 = 1 - x4
=>
3 - 3x2 + 5x2 = -1 => 2x2 = -4 => x2 = -2 => x1 = 1 + 2 = 3
3 - 3x4 + 5x4 = -5 => 2x4 = -8 => x4 = -4 => x3 = 1 + 4 = 5