Question About Parabola's

[usm_67]

plz help me out in this

The support for a bridge over a river is in the shape of an upside down (inverted) parabolic arch. At water level the arch is 30m wide. Max height of 10m above water. Equation?


Equation

y=a(x-h)^2+k

what is the equation plzz need the answer quick

 

[galactus]

You have the quation for a parabola, use it.

Center the parabola at the origin. The vertex will have coordinates (0,10), which is (h,k)

The edges at water level will have coordinates (15,0) and (-15,0), which is (x,y)

\(\displaystyle y=a(x-h)^{2}+k\)

\(\displaystyle 0=a(15-0)^{2}+10\)

Solve for a.