Challenge problem to the community - - - domain and range

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Discussion Overview

The discussion revolves around determining the domain and range of the relation defined by the equation y²(x² - 1) = x⁴. Participants explore the implications of this relation not being a function and examine the mappings of y based on different values of x.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants note that there is no one-to-one correspondence between x and y, leading to two different mappings, y₁(x) and y₂(x), which share the same maximal domain (R - {±1}).
  • Clarification is sought regarding the notation R - {±1}, with questions about its interpretation in terms of interval notation.
  • One participant questions whether specific values of x, such as -1/2 or 1/2, would yield real values for y, suggesting that y would be imaginary for these inputs.
  • There is a request for confirmation on whether x = 0 would provide a real value for y.

Areas of Agreement / Disagreement

Participants express differing interpretations of the domain notation and the implications of specific x values on the reality of y. The discussion remains unresolved regarding the correct interpretation of the domain and the nature of y for certain x values.

Contextual Notes

The discussion highlights potential ambiguities in mathematical notation and the need for clarification on the definitions used, particularly concerning the domain and the nature of the outputs based on chosen inputs.

checkitagain
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What are the domain and range of the following:
(Note: It is a relation that is not a function.)



[itex]y^2(x^2 - 1) = x^4[/itex]
 
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Since there's no one to one correspondence between a value for x and a value for y, you have 2 different mappings (functions in their own right). y_1 (x) and y_2 (x) with the same maximal domain (R-{+-1}). y_1 is minus 1 times y_2, for any allowable value of x.
 
dextercioby said:
Since there's no one to one correspondence
between a value for x and a value for y, you have 2 different mappings
(functions in their own right). y_1 (x) and y_2 (x) with the

[itex]> >[/itex] same maximal domain (R-{+-1}). [itex]< <[/itex]

y_1 is minus 1 times y_2, for any allowable value of x.
.



I take it you are only addressing the domain . . . for now.


With your notation, does (R - {+-1}) mean [itex](-\infty, -1) \ \ \cup \ \ (-1, 1) \ \ \cup \ \ (1, \infty) \ ?[/itex]


Or, does it mean [itex](-\infty, -1) \ \ \cup \ \ (1, \infty) \ ?[/itex]



I am asking you for your clarification before I comment further on the
possible/alleged correctness of your take on it. (I want to comment,
but I am waiting on some more information.)
 
I was too lazy to write down the LaTex code, but here goes

[tex]\mathbb{R} - \{\pm 1\}[/tex].
 
dextercioby said:
I was too lazy to write down the LaTex code, but here goes

[tex]\mathbb{R} - \{\pm 1\}[/tex].


What about x = -1/2 or x = 1/2, for instance?


Would those work or not?
 
dextercioby said:
No, y would be imaginary [itex]> > \ \ regarding \ \ x \ = -1/2 \ \ and \ \ x \ = 1/2 \ \ < < .[/itex]



checkitagain said:
(R - {+-1}) means [itex](-\infty, -1) \ \ \cup \ \ (-1, 1) \ \ \cup \ \ (1, \infty) \ ?[/itex]


Or, does it mean [itex](-\infty, -1) \ \ \cup \ \ (1, \infty) \ ?[/itex]

So, then, we must eliminate the first choice of interval notation
in the above quote box. Is the second choice of interval notation
in the quote box correct?


Can x = 0 give y as a real value or not?
 

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