( Enter your answer in the form of an equation for a vertical line of symmetry, not just a number.) 4. (1 point) The height y (in feet) of a ball thrown by a child is - 18 12 4 4x - 3 where a is the horizontal distance in feet from the point at which the ball is thrown. (a) How high is the ball when it leaves the child's hand? (Hint: Find y when x _. 0.) feet (b) What is the maximum height of the ball? feet (c) How far from the child does the ball strike the ground? feet the 5. ( 1 point)