Final answer:
f(x) = x^3 + x is an odd function because f(-x) = -f(x), supporting statement d) f(-3) = -f(3).
Step-by-step explanation:
An odd function satisfies the condition y(x) = -y(-x) for all x values in the domain. In this case, we need to determine if the function f(x) = x^3 + x is odd or even.
To check if it is odd, we substitute -x for x and simplify: f(-x) = (-x)^3 + (-x) = -x^3 - x.
Now, we compare f(-x) to -f(x): -f(x) = -(x^3 + x) = -x^3 - x.
Since f(-x) = -f(x), we can conclude that f(x) is an odd function. Therefore, the correct statement is d) f(-3) = -f(3).