Answer:
The ball will reach the ground when h=0.
Set the equation equal to 0.

Step-by-step explanation:
The height of a golf ball after it has been hit from the top of a hill can be modeled by the equation
,
where h is the height in feet and t is time in seconds.
When ball will reach the ground the distance between ball and ground is 0. So, the ball will reach the ground when h=0.
To find the time it takes for the ball to reach the ground, set the equation equal to 0 and use the Zero Product Property to solve for $t$.
Solve the equation using the Zero Product Property.
So, 
The 2-point form of the equation of a line can be written as ...
... y = (y2-y1)/(x2-x1)·(x -x1) +y1
For your points, this is ...
... y = (1-5)/(3-6)·(x -6) +5
... y = (4/3)(x -6) +5
It can also be written as
... y -5 = (4/3)(x -6)