Question 406879
  <pre><font size = 3 color = "indigo"><b>
Hi
A parabolic arch has a span of 100 feet and a maximum height of 25 feet. 
Using the vertex form of a parabola, {{{y=a(x-h)^2 +k}}} where(h,k) is the vertex
  y = a(x-50)^2 + 25  Vertex (50,25)
  0 = a50^2 + 25   |Using x-intercept Pt(0,0) to solve for a
 -25/2500 = a
  y = (-1/100)(x-50)^2 + 25
 height of the arch 20 feet from the center: 
 x = 30
 y = (-1/100)20^2 + 25
 y = -4 + 25
 y = 21ft