Modeling - Reciprocal Function

[Peter G.]

Hi, I am currently trying to model a set of data using a reciprocal function. I picked a couple of points, substituted the y and x values into two equations but I can't solve it!

Here is an example:

y = A / (Bx)

30 = A / (4.5B)

0.1 = A / (20B)

I tried solving it by all methods I know of but. For simplification purposes and to show evidence of my work I will show only one method:

From Equation 1: A = 135 B

Therefore, substituting into equation 2: 0.1 = 135 B / 20 B

The Bs cancel here and I can't get an answer.

Any help please?

Thanks!

 

[tjackson3]

Your version really only involves one constant, since A / (Bx) = (A/B) * (1/x) = C/x, where C = A/B. So you're essentially trying to fit two points to a one-parameter family, which isn't always guaranteed. I'd try writing y = A / (x + B). If you have three points, you can try y = A / (Bx + C), but that can just be reduced to the previous form. It might give you a better fit, though.