It is an upside down parabola. Vertex is (600, 50) ?

There are several methods. One of the simplest may be the completed squared form;

y=a(x-b)^2 + c

where (b,c) is the coordinates of the vertex.

In your case, the formula will be

y = -a(x-600)^2 + 50

The negative sign in front of the 'a' indicates that the parabola is 'upside down'
If another point besides the vertex were given, you can work out the value of a by replacing x and y by the respective given coordinates.

Thanks:)

You're welcomed! :)