Question 1086861
x-4y+z=11  [1]
4x+y-2z=5  [2]
x-4y+2z=9  [3]
Subtract [1] from [3]:
This gives z = -2
Substitute this value into [2] and solve for y in terms of x:
4x + y + 4 = 5
y = 1 - 4x
Use either [1] or [3] to solve for y:
x - 4(1 - 4x) - 2 = 11
17x = 17
x = 1
Thus y = 1 - 4*1 = -3
Ans A. The unique solution is 1, -3, -2