If xyz ≠ 0, is x (y + z) ≥ 0?
(1) │y + z│ = │y│ + │z│
(2) │x + y│ = │x│ + │y│
With 1) Z and Y should be both positive or both negative.
But we dont know the value of X == insuff
With 2) X and Y should be both positive or both negative.
But if both are negative and Z is positive and greater than Y, then equation is not satisfied. == insuff
Taking both together, XYZ can be all positive and all negative. This will satisfy the equation.