How can inverse functions help us find the range algebraically?

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Discussion Overview

The discussion centers on the use of inverse functions to find the range of a linear function algebraically. Participants explore the relationship between a function and its inverse, particularly in the context of one-to-one functions and the implications for determining ranges.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant presents the function y = 125 - 12x and asks for guidance on using inverse functions to find its range.
  • Another participant identifies the function as one-to-one and provides the inverse function, stating that the domain of the inverse is all real numbers, which implies the range of the original function is also all real numbers.
  • A different participant questions whether inverse functions can be found for functions that are not one-to-one and seeks clarification on the relationship between the domain of the inverse and the range of the original function.
  • Another participant notes that finding the inverse is not always straightforward and mentions the necessity of restricting the domain to ensure a one-to-one relationship, emphasizing the importance of graphical analysis and calculus for more complex functions.
  • A subsequent post seeks clarification on the concept of restricting a function's domain to create a one-to-one situation, questioning the common textbook explanation.

Areas of Agreement / Disagreement

Participants express differing views on the applicability of inverse functions to non one-to-one functions and the necessity of domain restrictions. The discussion remains unresolved regarding the generalizability of these concepts.

Contextual Notes

Limitations include the need for domain restrictions in certain cases to ensure one-to-one functions, and the complexity of applying these concepts to more intricate functions, which may require advanced mathematical tools.

mathdad
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Find the range algebraically.

y = 125 - 12x

There is a way to do this by finding the inverse function. Can someone show me how to apply the idea of inverse functions to find the range?
 
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$f(x)=125-12x$, a 1-1 function

inverse is $f^{-1}(x) = \dfrac{125-x}{12}$

the domain of $f^{-1}(x)$ is $\mathbb{R} \implies$ range of $f(x)$ is $\mathbb{R}$
 
This function is one-to-one. Can we find the inverse of functions that are not one-to-one?

You found the inverse of the given function.

You then said that the domain of the inverse is the range of the original function.

Correct?

Can this method be applied to all functions?
 
Finding the inverse of a function is not always easy.

Sometimes the domain of the function in question must be restricted to force a 1-1 situation.

This is the reason why graphical analysis is so important. More complex graphs require the concepts of calculus to analyze.
 
You said:

"Sometimes the domain of the function in question must be restricted to force a 1-1 situation."

I am not too clear in terms of restricting a function "to force a 1-1 situation."

What do you mean by this statement which is so common in textbooks?
 

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