Chapter 2 - Functions, Equations, and Graphs - 2-6 Families of Functions - Practice and Problem-Solving Exercises - Page 104: 16

$$y=f(x)-\frac{2}{3}$$

When $f(x)$ is translated $k$ units downward, the function's equation becomes $y=f(x)-k$. Thus, when $f(x)$ is translted $\dfrac{2}{3}$ unit down, the new function's equation is: $$y=f(x)-\frac{2}{3}$$