Answer:
8 seconds
Step-by-step explanation:
Set the equation equal to 0. Â You do this because h(0) means that there is no height of the object, and that then implies that the object is on the ground (where there is no height). Â Then factor using the quadratic formula:
[tex]0=-5t^2+40t[/tex]
Factor out the common constant and variable between the terms:
[tex]0=-5t(t-8)[/tex]
Solving for t, you get that t = 0 and t = 8. Â The t = 0 is indicative of the fact that at zero seconds (in other words before the object was launched) it was still on the ground. Â At t = 8, it had completed its parabolic travels and landed on the ground again. Â