Question

A track-and-field athlete releases a javelin. The height of the javelin as a function of time is shown on the graph below. Use the graph to complete the statements that follow. 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

Part 1:
 
 For this case we must see in the graph the axis of symmetry of the given parabola.
 We have then that the axis of symmetry is the vertical line t = 2.
 Answer:
 The height of the javelin above the ground is symmetric about the line t = 2 seconds:

 Part 2:

 For this case, we must see the time t for which the javelin reaches a height of 20 feet for the first time.
 We then 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, observing the graph we see 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