A suspension bridge has two supporting towers with a cable secured at either end of the span and then draped between the towers. In the section between the two supporting towers, the cable forms a parabolic curve. At the lowest point of the
curve, the cable is 20 feet from the surface of the bridge. The supporting towers
are 500 feet apart, and rise 420 feet from the surface of the bridge to the top of the tower. Use the height of the left tower as the y-intercept.

4. What are the vertex and the y-intercept?

5. What is the equation in verter form of the suspension cable?