Since this is multiple choice ...
• check if B is correct:
x = 0, y = 4, z = 1 ⇒ 3x - y + 4z = -4 + 4 = 0 ≠ -10
(it's not)
• check if C is correct:
x = -2, y = 4, z = 0
⇒ 3x - y + 4z = -6 - 4 + 0 = -10
⇒ 3x - y + 4z = 2 + 4 + 0 = 6
⇒ 3x - y + 4z = -4 - 4 + 0 = -8
While this solution does satisfy the system, it can still have infinitely many other solutions that would work.
• check if D is correct:
Eliminate one of the variables from each equation. For instance,
(3x - y + 4z) + (-x + y + 2z) = -10 + 6
2x + 6z = -4
x + 3z = -2
and
(2x - y + z) + (-x + y + 2z) = -8 + 6
x + 3z = -2
but now it's impossible to eliminate one of the variables.
Therefore there are infinitely many solutions to the system [D].
