SOLUTION: An arch is in the shape of a parabola. It has a span of 180 meters and a maximum height of 15 meters. What is the equation of the parabola? Please and thank you, I'm totally stu

Place the origin of the coordinate system on the ground level under at the vertex of the parabola, 
i.e. under the top point of the arc.


Let x be horizontal axis and y be the vertical axis, directed up.


Then the equation of the parabola is  y = -ax^2 + 15.


Then the span of the parabola is from x = -90 m to x= 90 m.


Hence,  y = 0 = ,   or


    a*90^2 = 15,

    a =  =  =  = .


Thus the equation of the parabola is  y = .   ANSWER