Aproblem involving a ball being thrown in the air is modeled with a quadratic function which of the following would you be solving for if asked to find the time at which the ball reaches maximum height a) an x-intercept of the graph b) the y-intercept of the graph c) the x-coordinate of the vertex d) the y-coordinate of the vertex

You would be looking for the y-coordinate of the vertex (D).

In equations for physics problems like this, x always represents time. Since height is not a time, then we can ignore all x answers.

y will represent height in these problems, but we have to determine which we are looking for. The y-intercept would be when x = 0, or time = 0. This would be the initial height of the ball. Since we are assuming that it gets thrown up into the air, this is not what we are looking for. Therefore, we need the vertex's y-coordinate.