Suppose an arrow is shot upward on the moon with a velocity of 39 m/s, then its height in meters after t seconds is given by h(t)=39t-0.83t^2. Find the average velocity over the given time intervals.

[8, 9]:

[8, 8.5]:

[8, 8.1]:

[8, 8.01]:

[8, 8.001]:

I understand that you need to figure out slope and simplify but my answer never comes out correctly.