Abuilding has an entry the shape of a parabolic arch 52ft high and 42ft wide at the base. find an equation for the parabola if the vertex is put at the origin of the coordinate system.

The description expresses three points which can be used for a standard form equation. The vertex is stated to be (0,0) and is a maximum; two other points are (-21,-74) and (21,-74)
The equation for vertex form of a parabola:
y=a(x-h)^2+k
vertex (h,k)
thus our equation will be:
y=a(x-0)^2+0
thus
y=ax^2
using one of the points, the value of a will be:
-74=a(21)^2
a=-74/441
thus the equation will be:
y=-74/441x²

Ab=dc ac=de ad=bce i hope this !