Question

The height of the javelin above the ground is symmetric about the line t = seconds. The javelin is 20 feet above the ground for the first time at t = seconds and again at t = seconds

Answer 1

I FOUND YOUR COMPLETE QUESTION IN OTHER SOURCES.
PLEASE SEE ATTACHED IMAGE.

Part 1:

we must see in the graph the axis of symmetry of the given parabola.
The axis of symmetry is the following vertical line:

`t = 2`
Answer:
The height of the javelin above the ground is symmetric about the line t = 2 seconds:

Part 2:

we must see the time t for which the javelin reaches a height of 20 feet for the first time.
We have that when evaluating t = 1, the function is:

`h (1) = 20.`
To do this, just look at the graph.
Then, we must observe the moment when it returns to be 20 feet above the ground.
For this, we have from the graph that:

`h (3) = 20 feet`
Therefore, a height of 20 feet is again reached in 3 seconds.
Answer:
The javelin is 20 feet above the ground for the first time at t = 1 second and again at t = 3 seconds