Question

A soccer ball is kicked upward and follows a trajectory modeled by the function h(t)=-4t^2+16t+20. After how many seconds will the ball hit the ground?

Answer 1

h(t)=4(-t²+4t+5)=0 when the object hits the ground.

Therefore t²-4t-5=0=(t-5)(t+1), so when t-5=0, t=5 seconds (t=-1 is negative time, time before the ball is kicked).