Answer:
9
Step-by-step explanation:
We know that
[tex]h(t)=-16t^2+1296[/tex]
The balls hits the ground when h(t)=0, so
[tex]-16t^2 + 1296=0 \\ \\ t^2 - 81=0 \\ \\ t^2 = 81 \\ \\ t=9[/tex]
Note I only considered the positive case because time must be positive.
