As you are using a laser speed gun I will assume ‘y’ is equivalent to velocity and ‘x’ is time.
V = -0.0017t^5 + 0.042t^4 -0.4432t^3 + 2.4625t^2 + 2.1189t + 10.315

We can see that at t=0 velocity is 10.315 m/s

Differentiating wwt time gives:
dv/dt = acc(t) = -0.0085t^4 + 0.168t^3 -1.3296t^2 + 4.925t + 2.1189

We can see that at t=0 acceleration is positive and maximum velocity is reached when dv/dt = 0 which is approximately 10.25 secs

My experience with the stalker radar gun is that the velocity data is very noisy. With results being highly dependent on the filtering used, such that results cannot be compared between studies or test sessions unless they use similar filtering. Matt Cross (a former student at AUT) did some work on standardize filtering of raw velocity data for measuring athlete sprinting performance. Sprinting was commonly over 30 meters with variables of interest including peak acceleration, maximum velocity and power profile.

Matt Cross et al. (2015) International Journal of Sport Physiology and performance, 10, 695-702

hope this helps