I apologize. I put this up and then realized the solution. Please delete this.
Find the critical points.
So I set the derivatie to 0, to find the critical points, and got:
... looks like some kind of spooky quadratic equation.
I know I need to find how those 2 equal 0.
I don't know how, aside from lots of trial and error.
edit: solution [SIZE="7"]GRAPH!