On mathematical problems of quadratic function Fenghuang bridge on Qingjiang River in Enshi has been completed and opened to traffic. Fenghuang bridge is a half through reinforced concrete arch bridge integrating highway traffic and urban landscape. The arch of the main bridge draws a beautiful arc in the air. From a distance, it looks like a curved rainbow lying on Qingbo (as shown in the picture). The arch of the bridge is a part of parabola, The arch height and span above the bridge are about 18 meters and 112 meters respectively (1) Please establish an appropriate plane rectangular coordinate system and find an analytical formula that can approximately describe the arch shape of the main bridge; (2) Calculate the length of the vertical support 28 meters from the center of the bridge deck

On mathematical problems of quadratic function Fenghuang bridge on Qingjiang River in Enshi has been completed and opened to traffic. Fenghuang bridge is a half through reinforced concrete arch bridge integrating highway traffic and urban landscape. The arch of the main bridge draws a beautiful arc in the air. From a distance, it looks like a curved rainbow lying on Qingbo (as shown in the picture). The arch of the bridge is a part of parabola, The arch height and span above the bridge are about 18 meters and 112 meters respectively (1) Please establish an appropriate plane rectangular coordinate system and find an analytical formula that can approximately describe the arch shape of the main bridge; (2) Calculate the length of the vertical support 28 meters from the center of the bridge deck

(1) If the center point of the bridge deck is taken as the origin and the bridge deck is taken as the X axis, then y = - 9x ^ 2 / 1568 + 18
(2) When x = | 28 | y = 13.5