Question 350709
When a ball is thrown, its height in feet h after t seconds is given by the equation 
h=vt-16t^2 
where v is the initial upwards velocity in feet per second. If v=9 feet per second, find all values of t for which h=1 foot. Do not round any intermediate steps. Round your answer to 2 decimal places.
.
h=vt-16t^2 
Substitute in the value for v:
h=9t-16t^2 
Substitute in the value for h:
1=9t-16t^2 
Solving for t:
1=9t-16t^2 
16t^2+1=9t 
16t^2-9t+1=0
Solve using the quadratic formula.  Doing so yields
t = {0.41, 0.15} seconds
.
Detail of quadratic follows:
*[invoke quadratic "t", 16, -9, 1 ]