For f(x) = 5x -4, the slope is 5 and the y-intercept is 4.

__For any two cotangent lines, we know:__

**1. **The
slopes are opposites. Thus, the slope of the second line must
be -5.

**2.**
The sum of the y-intercepts is 1. Thus 4 + b = 1. The y-intercept of the second line is -3.

So, the second cotangent line is represented
by the function g(x) = -5x - 3**.** A graph of
f, g, and fg is below.