A Ball Is Thrown Upward in Such a Way That $H ( t ) = - 16 t ^ { 2 } + 64 t + 80$

Short Answer

A ball is thrown upward in such a way that t seconds later, it is $H ( t ) = - 16 t ^ { 2 } + 64 t + 80$ feet above the ground. How many seconds later does the ball hit the ground?