Solve each system using matrix notation. Express the solution set using vectors.
(a) 3x + 2y + z = 1
x - y + z = 2
5x + 5y + z = 0
(b) x + y - 2z = 0
x - y = -3
3x - y - 2z = -6
2y - 2z = 3
(c) 2x - y - z + w = 4
x + y + z = -1
(d) x + y - 2z = 0
x - y = -3
3x - y - 2z = 0