Trouble finding the Linear Functions that satisfy the given Identity

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Homework Help Overview

The discussion revolves around finding linear functions that satisfy the identities f[f(x)] = 2x + 1 and f[f[f(x)]] = 2x + 1. Participants are exploring the properties of linear functions in this context.

Discussion Character

  • Exploratory, Mathematical reasoning

Approaches and Questions Raised

  • The original poster expresses uncertainty about how to approach the problem. Another participant suggests starting with the assumption that f(x) is a linear function of the form ax + b and attempts to derive relationships for a and b based on the given identities.

Discussion Status

Some participants have provided hints and initial attempts at solving the first identity, while the second identity remains unaddressed. There is acknowledgment of potential solutions for the first problem, but no consensus on the correctness of these solutions.

Contextual Notes

Participants note that a and b may not be rational numbers, which introduces complexity into the problem. The original poster has not yet attempted the second identity.

SolXero
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Homework Statement



Given f[f(x)] = 2x + 1 find all linear functions that satisfy this identity.
Given f[f[f(x)]] = 2x + 1 find all linear functions that satisfy this identity.


2. The attempt at a solution

I have not started to attempt a solution at this because I have no idea how to do these types of problems.
 
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SolXero said:

Homework Statement



Given f[f(x)] = 2x + 1 find all linear functions that satisfy this identity.
Given f[f[f(x)]] = 2x + 1 find all linear functions that satisfy this identity.


2. The attempt at a solution

I have not started to attempt a solution at this because I have no idea how to do these types of problems.
You're give that f(x) is a linear function, so let f(x) = ax + b.
For the first problem, you know that f(f(x)) = 2x + 1, so f(ax + b) = 2x + 1, or a(ax + b) + b = 2x + 1. Solve for a and b. Hint: a and b are not rational numbers.

Solve the second problem in a similar manner.
 
Thanks a lot!

For the first problem the answer would be:

f(x) = √2x + (-1+√2) and
f(x) = √2x + (-1-√2)

right?

I have yet to do the second one.
 

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