Answer:
Step-by-step explanation:
Your position equation is given as
[tex]h(t)=-16t^2+391t+3[/tex]
If you would like to find the time(s) that the object is 619 feet high, we have to fill in h(t) with 619 and do the algebra:
[tex]619=-16t^2+391t+3\\0=-16t^2+391t-616[/tex] and then factor. It's easiest to use the quadratic formula for this. The 2 times are t = 1.7 s, 22.7 s
If we want to know how long the object is in the air, set h(t) equal to 0 and factor. Again, use the quadratic formula and the time is 24.4 s