s(t) = -16t^2 - 1000,

which gives the height, in feet, of an object that has fallen for t seconds from a height of 1000 feet. The velocity at time t = a seconds is given by:

lim

(t -> a)

__s(a) - s(t)__

a - t

If anyone can explain to me how to do this I would be very appreciated of.

Thank you.