Physics semester one abbott?

Question

A position of a runner is given by x=4.10t-0.500t^2, where x is in meters and t is in seconds. What is the average speed between t=0 and t= .820 s?

Answer 1

3.69 m/s.
x = v0*t + at^2/2
v0 = 4.1
a = 2*-0.5 = -1
t = 0.82
v1 = v0+at = 3.28
v(ave) = (v0+v1)/2 = 3.69