# Is there an equation?

• Apr 21st 2006, 10:15 AM
jeffeff
Is there an equation?
I hope I can describe this well enough so that someone might be able to help me.

I'm looking for a general equation that includes, for example, the following coordinates:

(0,0)
(1,1)
(3,2)
(6,3)
(10,4)

I've figured out two ways to describe what I want. Either x = the sum of all y's less than or equal to it, or x = y plus the x immediately preceding it in the series.

I'd be most interested in whether this could be graphed as a curve.

Thanks in advance, and I hope this is clear.

Jeff Eff
• Apr 21st 2006, 10:49 AM
Jameson
Both of your explanations work, but I don't think you'll be able to graph those kinds of "functions" on any graphing utility because they are not standard ones, like sin(x), ln(x), sqrt(x), etc.
• Apr 21st 2006, 05:18 PM
Ranger SVO
I think you can. Gragh the following equation

f (x) = [sqrt(8*x+1)-1] / 2

If you look at your points, you should be able to see a quadratic equation only in reverse. (0,0) (1,1) (2,3) (3,6) (4,10)

The equation should be y = 0.5x *(x + 1), now solve for x and you should get what you want to graph

If you want the other half of the graph you will also have to graph -f(x)
• Apr 22nd 2006, 06:18 AM
Ranger SVO
http://i7.photobucket.com/albums/y284/wrf01a/graph1.jpg

Without access to an equation editor, my previous post might be confusing
• Apr 22nd 2006, 06:27 AM
Jameson
Oh nice catch! I didn't mean that there wasn't an answer, just that the two explanations the OP gave couldn't be graphed in that way on something like you did - the TI-89 (good calculator!).
• Apr 23rd 2006, 10:12 AM
jeffeff
Thank You!
Yay!

That's what I was looking for. It's been awhile since I've done this kind of thing.

Jeff Eff