Finding the Range of a Function Using Graphs

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Discussion Overview

The discussion revolves around finding the range of the function y = 125 - 12x^3 using its graph. Participants explore methods for determining the range, including the use of inverses and the challenges associated with more complex functions.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification, Debate/contested, Homework-related

Main Points Raised

  • One participant suggests that the range can be determined by looking at the values of y, indicating that y can take on all real numbers.
  • Another participant notes that while the function in question is straightforward, the method of finding the range through the inverse function could be applied to more complicated functions.
  • There is a recognition that finding the inverse of a function can be challenging, with one participant mentioning the use of external tools like Wolfram to assist in this process.
  • It is pointed out that not all functions possess an inverse, and calculus offers various techniques for graphing functions.

Areas of Agreement / Disagreement

Participants generally agree that the range of the given function is all real numbers, but there is no consensus on the ease of finding inverses for more complicated functions, highlighting differing views on the challenges involved.

Contextual Notes

Some participants express uncertainty regarding the applicability of inverse functions to more complex cases and the limitations of their methods, particularly in relation to functions that do not have inverses.

Who May Find This Useful

This discussion may be useful for students learning about function ranges, graphing techniques, and the concept of inverses in precalculus and calculus contexts.

mathdad
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Set 3.1
Question 16.

Find the range using the graph of y.

y = 125 - 12x^3

Obviously, I must graph the function as step one. How is the graph used to find the range?
 
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you look at the values of $y$ ... $y \in (-\infty,\infty)$

[DESMOS=-6.723253753255145,6.375413083862618,-819.3444017457867,753.6024560560803]y=125-12x^3;[/DESMOS]
 
From the graph, I can see that it is ok for y to be ALL REAL NUMBERS. Of course, this is an easy function. What about for complicated functions? Can I apply the method of taking the inverse? The domain of the inverse function is the range of the original.
 
if you can find the inverse ... sometimes easier said than done
 
You have made it clear that finding the inverse can sometimes be overwhelmingly difficult. In terms of complicated functions, I use wolfram to find the inverse.
 
Not all functions have an inverse. Calculus provides several tools for sketching the graph of a function.
 
Thank you everyone for your help. You will see less questions from now on as I use the free youtube clips to review precalculus.
 

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