Chapter 2.1, Problem 23E

For the following exercises, consider an athlete running a 40-m dash. The position of the athlete is given by $d\left(t\right)=\frac{t^3}{6}+4t$ , where d is the position in meters and t is the time elapsed, measured in seconds.

23. Use the preceding exercise to guess the instantaneous velocity of the runner at t = 2 sec. For the following exercises, consider the function $f\left(x\right)=\left|x\right|$ .