Final answer:
The function y = 3 - x^3 is nonlinear because it does not represent a straight line.
Step-by-step explanation:
The function y = 3 - x^3 is nonlinear because it does not represent a straight line. In a linear function, the highest power of the independent variable is 1. However, in this function, the highest power of x is 3, which makes it a nonlinear function.