Answer:
t = [0.493,4.2]
Step-by-step explanation:
The height of the rocket straight up into the air is given by :
[tex]h(t)=-16t^2+85t+5[/tex]
We need to find the interval the rocket be at least 43 feet above the ground.
[tex]43\ge -16t^2+85t+5\\\\t\ge 0.493\ and\ t\le 4.82\ s[/tex]
So, the required interval during which the rocket is at least 43 feet above the ground is [0.493,4.2].
