Final answer:
The equation that best compares the slopes of the two functions is option D, f(x) = x + 18.
Step-by-step explanation:
The equation that best compares the slopes of the two functions is option D, f(x) = x + 18.
The slope of a linear function is represented by the coefficient of the x-term. In option D, the coefficient of x is 1, which means the slope is 1. This slope is greater than the slopes of options A, B, and C.
For example, in option A, the coefficient of x is -9, which means the slope is -9. Since -9 is less than 1, option D has a steeper slope.