Change of Variables(nonlinear function to a linear one)

In summary, the conversation discusses the process of converting a nonlinear model, given as f(x) = \frac{ax}{b+x}, into a linear one using change of variables. The attempted solutions involve taking the reciprocal of both sides and using log transformation, but with the issue of x being in the denominator. An alternative solution is suggested using matrix form, rewriting the equation as b*f(x) - ax = x*f(x).
  • #1
HclGuy
13
0

Homework Statement


I'm given a nonlinear model which I am trying to perform a linear regression on. I need to use change of variables in order to convert the nonlinear model into a linear one.

Homework Equations


I am given [tex]f(x) = \frac{ax}{b+x}[/tex] where a and b are just parameters.
I need to use change of varibles to change this function into a form of [tex]F(x) = AX + B[/tex]

The Attempt at a Solution


I have tried to take the reciprocal of both sides to get
[tex]\frac{1}{y} = \frac{b+x}{ax} = \frac{b}{ax} + \frac{1}{a}[/tex] , only problem with that is that the x is in the denominator. I have also tried using log transformation to both sides without success. Any help is appreciated thanks!
 
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  • #2
see below
 
Last edited:
  • #3
I would rewrite it as b*f(x) - ax = x*f(x)

or in matrix form

[tex] \left(\begin{array}{cc}x_{1}&f(x_{1})\\x_{2}&f(x{2})\\.&.\\.&.\\.&.\\x_{n}&f(x_{n})\end{array}\right) \left(\begin{array}{cc}-a\\b\end{array}\right) = \left(\begin{array}{cc}x{1}*f(x_{1})\\x{2}*f(x{2})\\.\\.\\.\\x_{n}*f(x_{n})\end{array}\right)[/tex]
 

1. What is a change of variables?

A change of variables is a mathematical technique used to transform a set of variables into another set of variables. This is typically done to simplify a problem or make it easier to solve.

2. Why is a change of variables necessary?

A change of variables is necessary when dealing with complex or nonlinear functions. It allows us to transform the variables into a new set that is easier to work with and may reveal patterns or relationships that were not apparent before.

3. How do you perform a change of variables?

To perform a change of variables, you first need to identify the variables in the original function. Then, you choose a suitable transformation that will convert these variables into a new set. This can be done using algebraic methods or geometric transformations.

4. What are the benefits of using a change of variables?

A change of variables can make a problem more manageable and can lead to a better understanding of the underlying relationships between variables. It can also simplify the mathematical calculations needed to solve a problem.

5. Are there any limitations to using a change of variables?

While a change of variables can be a powerful tool, it is not always applicable or appropriate. The transformation chosen must be valid for the given problem and may introduce new complexities. Additionally, the resulting linear function may not accurately represent the original nonlinear function in all cases.

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