Finding Level Curves of f(x,y)=xy

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Discussion Overview

The discussion revolves around finding the level curves of the function f(x,y) = xy for various values of c, specifically c = ±1, ±2, ±3, ±4, ±5. Participants explore the implications of the function's definition and the restrictions on the variable x.

Discussion Character

  • Exploratory
  • Mathematical reasoning

Main Points Raised

  • One participant proposes that setting f(x,y) = c leads to the equation c = xy and suggests that y can be expressed as y = c/x, identifying this as a hyperbolic function.
  • Another participant questions the restriction of x to positive values, arguing that unless specified, x can take any non-zero value, including negative values.
  • A different participant clarifies that the restriction mentioned arises from the denominator in the expression y = C/x, which becomes undefined if x is zero.
  • Another participant agrees that x can be any non-zero number, emphasizing that it does not have to be positive.

Areas of Agreement / Disagreement

Participants express disagreement regarding the restrictions on the variable x, with some asserting that x must be positive while others argue that it can be negative as long as it is not zero.

Contextual Notes

The discussion highlights the ambiguity surrounding the restrictions on x and the implications for the level curves, particularly in relation to the function's definition and the mathematical operations involved.

ozgurakkas
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Question as follows

f(x,y)=xy , find the level curves for c= +-1,+-2,+-3,+-4,+-5

My first attempt was to set f(x,y)=c

c=xy and y=1/x C and this is an hyperbolic function. Is that right?

I am also confused what values x can get. I know it is restricted and x>0.
Can x get the same value as C ?
 
Last edited:
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ozgurakkas said:
Question as follows

f(x,y)=xy , find the level curves for c= +-1,+-2,+-3,+-4,+-5

My first attempt was to set f(x,y)=c

c=xy and y=1/x C and this is an hyperbolic function. Is that right?

I am also confused what values x can get. I know it is restricted and x>0.
Can x get the same value as C ?
Why is it restricted to x> 0? Unless something else is said, y= C/x is only restricted to x not 0. Other than that, x can have any positive or negative value whatever C is.
 
Question does not say it is restricted. I said it because x is in the denumerator. if it is 0 then it is undefined.
 
Yes. But not being 0 does not mean it must be positive! x can be any positive or negative number.
 

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