Atunnel is in the shape of a parabola. the maximum height is 31 m and it is 13 m wide at the base as shown below.
a parabola opening down with vertex at the origin is graphed on the coordinate plane. the height of the parabola from top to bottom is 31 meters and its width from left to right is 13 meters.
what is the vertical clearance 2 m from the edge of the tunnel?

Using the given values from the problem and the illustration, three points are known which are (0,0), (6.5,-31), (-6.5,-31). The first step in solving this problem is to determine the equation of the parabola.
y = ax²
-31 = a(6.5)²
-31 = 42.25a 
a = -31/42.25 
a = -124/169 

Therefore, the equation of the parabola is y = (-124/169)x². The value 4.5 is then substituted in the equation as x to get the answer which is 16.14 meters.