Question 909873
h(t) =-16t^2+48t+864 
0 = -16t^2+48t+864 
0 = -16(x-3/2)^2 + 36 + 864
16(x-3/2)^2 = 900
x = 3/2 + 15/2= 9sec
{{{drawing(300,300,   -10,100,-10,1000,  
 grid(1),
graph( 300, 300, -10,10,-100,1000,0, -16x^2 + 48x + 864 ))}}}