If x + y + z = 0, then what is the value of xy + yz + zxx^2 + y^2 + z^2?

Answer: Option D

Given, x + y + z = 0
By putting values x = 2, y = -1, z = -1
$$\begin{array}{rl}& \text{Now, }\frac{xy+yz+zx}{x^2+y^2+z^2}\\ & =\frac{-2+1-2}{4+1+1}\\ & =\frac{-1}{2}\end{array}$$