Does anyone know a good software or web service where you can draw a graph an get the formula?

Like: I input three points: (0,0), (6,9), (10,10). Then I see a curve that perfectly intersects those three points and get the formula for it.

There are a lot of situations in game developement when that would be useful. Like if you want the speed of something slowly start rising, and then rise faster and faster until it stabilizes and then start rising slower and slower until its not rising anymore. Things like that. If you could just visualize this variation of speed on a graph and get the formula to implement in your game would be awesome.