Answer :
Answer:
The present was 300 feet above ground 5 seconds after being thrown.
6.47 seconds passed before the present hit the ground.
Step-by-step explanation:
We have the following quadratic function
[tex]h(t) = -16t^{2} - 20t + 800[/tex]
Which determines the height of the present.
Determine when the present was 300 feet above the ground.
This is when [tex]h(t) = 300[/tex]. So
[tex]h(t) = -16t^{2} - 20t + 800[/tex]
[tex]300 = -16t^{2} - 20t + 800[/tex]
[tex] -16t^{2} - 20t + 500 = 0[/tex]
This is [tex]t = -6.25[/tex] and [tex]t = 5[/tex]. There are no negative time instants. So the present was 300 feet above ground 5 seconds after being thrown.
Determine how many seconds passed before the present hit the ground.
This is t when [tex]h(t) = 0[/tex]
[tex]h(t) = -16t^{2} - 20t + 800[/tex]
[tex]-16t^{2} - 20t + 800 = 0[/tex]
[tex]t = 6.47[/tex]
6.47 seconds passed before the present hit the ground.