I'm pretty new to Mathematica.

I'd like to show the intersection points in my graphic.

These are my inputs:

f[y_] := -10 x^2 + 4000 x;

NSolve[f[y] == 144000, x]

Plot[{f[y], 144000}, {x, 0, 400}, PlotRange -> {0, 400000}]

Thanks for your help!

puckie