The position of an object at time t is given by s(t) = -8 - 9t. find the instantaneous velocity at t = 1 by finding the derivative. using the limit formula to find the derivative

Ughhh...the limit formula...this should be thrown in the trash the minute you start doing derivatives :P

(-8-9(t+d)-(-8-9t))/(t+d-t)

(-8-9t-9d+8+9t)/d

-9d/d  (which is -9 for any value of d as well as when d approaches zero)

-9

So the instantaneous velocity is regardless of t or delta t