Question

The following equation models the height (h), of a rocket (t) seconds after it was launched from the ground.
h=-16t^2+90t

How long will it take the rocket to return to the ground?

Answer 1

When the rocket returns to the ground you are at h=0 thus solve for t when 0=-16t^2+90t

Answer 2

\[t=-90\pm \sqrt{90^2-4(-16)(0)}/2(-16)=(-90\pm 90)/(-32)\] which clearly you have t=0 which is when it is going to be launched and t=5.625 when it returns to the ground

Answer 3

thanks!

Answer 4

You are welcome :-)