<p>
I'm pretty new to Mathematica.<p>
I'd like to show the intersection points in my graphic.<p>
These are my inputs:

f[y_] := -10 x^2 + 4000 x;<p>
NSolve[f[y] == 144000, x]<p>
Plot[{f[y], 144000}, {x, 0, 400}, PlotRange -> {0, 400000}]<p>

Thanks for your help!<p>
puckie