Question 252842
A missile is fired vertically into the air. The distance s (in feet) above the ground as a function of time t (in seconds) is given by the equation below.
h(t)=300+500t-16t^2
h(t) is the height of the missile after "t" seconds.
h(0) = 300 is the height from which the missile is launched.
---
(a) When will the missile hit the ground?
When the missile hits the ground the height is zero.
Solve 300 + 500t - 16t^2 = 0
75 + 125t - 4t^2 = 0
t = [-500 +- sqrt(500^2-4*-4*300)]/-8
t = 31.85 seconds

(b) When will the missile be 1000 feet above the ground? 
h(t)=300+500t-16t^2
300+500t-16t^2 = 1000
-16t2 + 500t - 700 = 0
-4t^2 + 125t - 175 = 0
Use the quadratic formula to get:
x = 29.79 seconds (on the way down)
x = 1.46 seconds (on the way up)
======================================
Cheers,
Stan H.

-----------------------