Question

A parabolic arch has a height of 20 m and a width of 36 m at the base. If the vertex of the parabola
is at the top of the arch, at which height above the base is it 18 m wide?

Answer 1

clearly the equation of the arch is

y = 20 - ax^2
y(18) = 0, so
a = 0.0617
So, y = 20-0.0617x^2

y(9) = y(-9) = 15

Answer 2

Thu