Answer:

Explanation:
We know that the equation that models the height of the ball as a function of time is
.
Where the initial speed is 80 feet.
When the ball lands on the ground, its height will be
.
So to know how long it will take the ball to reach the ground, equal h (t) to zero and solve for t.

To solve this quadratic equation we use the quadratic formula.
For an equation of the form:

The quadratic formula is:

In this case

Then


We take the positive solution
