Write out the augmented matrix for the following linear systems. Then solve the system by first applying elementary row operations of type #1 to place the augmented matrix in upper triangular form, followed by Back Substitution.
(a) x1+7x2 =4
- x1 - 9x2 = 2
(b) 3z - 5w = -1
2z + u> = 8
(c) x - 2y + z = 0
2y - 8z = 8
-4x +5y + 9z = -9
(d) p + 4q-2r=l
-2p - 3r = -7
3p - 2q + 2r = -l
(e) x1 - 2x3 = -1
x2 - x4 = 2
-3x2 + 2x3 = 0
-4x1 + 7x4 = -5
(f) -x + 3y - z + w = -2
x - y + 3z - w = 0
y - z + 4w =
7 4x - y + z = 5