Plot[4*10^(14) x/( (6.4*10^6+x)6.4*10^6 ) - 1/2 (Pi / 43200)^2 (2*6.4*10^6 x+ x^2) ,{x,1,10^9}]

Uh oh! Wolfram|Alpha doesn't run without JavaScript.

Please enable JavaScript. If you don't know how, you can find instructionshere.Once you've done that, refresh this page to start using Wolfram|Alpha.