Answer
k(x) = $-\frac{4}{5}$x -2
Work Step by Step
1. Remember we are writing the function in the form f(x) = ax+b.
2. Since a = rate of change and rate of change in this case = $-\frac{4}{5}$, we have k(x) = $-\frac{4}{5}$x+b.
3. Since the initial value is the value when x = 0 (the y-intercept), which = b, we know that b = -2
4. We now have k(x) = $-\frac{4}{5}$x -2