Final answer:
The equation of the translated function is f(x) = 2x - 4 (option A).
Step-by-step explanation:
The equation that represents a translation of the parent function 4 units down is f(x) = 2x - 4 (option A).
To translate a function 4 units down, we subtract 4 from the original function's y-coordinate (f(x)). In this case, the original function is f(x) = 2x.
For example, if we have a point (x, y) on the original function, the translated point would be (x, y-4). So, the translated function is represented by f(x) = 2x - 4.