Answer:
6 .74 seconds
Step-by-step explanation:
The height of the ball is given by the equation:
[tex]R(x) = - 16( {x}^{2} - 5x - 6)[/tex]
When the ball hit the ground, then;
[tex]R(x) = 0 \\ - 16( {x}^{2} - 5x - 6) = 0 \\ {x}^{2} - 5x - 6 = 0 \\ x = -0.74 \: Or \: 6.74[/tex]
We discard x=-0.74 since time is not negative.
Therefore the ball hit the ground after 6.74 seconds.