**A balloonist drops a sandbag from a balloon
160 feet above**

15-) A balloonist drops a sandbag
from a balloon 160 feet above the ground. After t seconds, the sandbag is 160
-t^2 feet above the ground.

a-) find the velocity of the sandbag at t = 1.

b-) With what velocity does the sandbag strike the ground.

19-) Find the average rate of change of y with respect to x on the given
interval.(b) Find the instantaneous rate of change of y with respect to x at
the left endpoint of the interval.

y =x^2 + 2 ; [3, 3.5]

3-) Use the f'(x)= lim (h-0) f(x + h) - f(x)/h to find f'(x). b-) Find the
domain of f'. c) Find and equation of the tangent line to the graph of f at P.
d) Find the points on the graph a which the tangent line is horizontal.

f(x) = x^3 + x ; [1,2]