Question

The position of an object at time t is given by s(t) = -4 - 2t. Find the instantaneous velocity at t = 6 by finding the derivative.

Would the derivative be -16?

This is my work:
To find the derivative first I solved for s(t) replacing the 't' values with 6.
s(t) = -4 - 2(6)
s(t) = -16

Afterwards, I solved for (t+h)
s(t) = -4 - 2(6+h)
s(t) = -4 - 12 - 2h
s(t) = -16 - 2h/h
s(t) = -16