Question

The height of a projectile, fired straight up is given by the equation s(t)=-16t^2+64t+80, where t is in seconds and h(t) is in feet. What was the initial height of the projectile and how long until the projectile hit the ground?

Answer 1

what is the height when t=0?

for the second part, you need to find when the parabola crosses the x axis; you need to set the equation equal to 0.