Henry is building a model of the Clifton Suspension Bridge using a scale factor of 100 ft: 1 in. The cables between the towers are in the shape of a parabola. He writes an equation of the parabola to describe the model he is building and uses the equation to determine the distances from the cable to the deck of the bridge Suppose the deck is the x-axis and the vertex lies on the y-axis. What is the equation that Henry writes?