Need help with some function for my game

Hello, guys and gals, sorry for my english. I'm making a little game but I'm a little stuck in its economy, to continue I need the functions that give me this :

http://i.imgur.com/RIfUZ.jpg

http://i.imgur.com/FYBy8.jpg

Thanks in advance for any help (Talking)

Re: Need help with some function for my game

first graph ... $\displaystyle y = \frac{k}{x}$ where k is a constant should work

second graph ... one possible curve; Logistic function - Wikipedia, the free encyclopedia

Re: Need help with some function for my game

Thanks for your help.

Is there some site where I can play around with functions and their constants and see the resulting graph live ? (I know how to google but I suppose you already have some handy one in mind, heh)

Re: Need help with some function for my game

You can get nice graphing utility, for free, here:

Graph | Plotting of mathematical functions

Re: Need help with some function for my game

Re: Need help with some function for my game

Sorry for the bump but I'm trying to find a function to give me the second one, but I just can't ...

Draw Function Graphs - Plotter

Something like the bottom picture in this page :

Team:Imperial College/Growth Curve - 2008.igem.org