By Continuity definition 1/0 is infinity

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Discussion Overview

The discussion revolves around the interpretation of the limit of the function 1/x as x approaches 0, specifically addressing the implications of continuity and the definition of limits in this context. Participants explore whether 1/0 can be considered infinity based on continuity definitions and the behavior of the function near the discontinuity at x=0.

Discussion Character

  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant argues that since the limit of 1/x as x approaches 0 is infinity, and the function is continuous, it follows that 1/0 should be considered infinity.
  • Another participant counters that 1/x is not defined at x=0, which means continuity cannot be applied as the function is not defined at that point.
  • Some participants note that the left-hand limit approaches negative infinity while the right-hand limit approaches positive infinity, indicating that the limit does not exist in the traditional sense.
  • There is a discussion about the nature of discontinuity at x=0, with references to the graph of y=1/x illustrating the behavior of the function around that point.

Areas of Agreement / Disagreement

Participants generally disagree on the interpretation of the limit of 1/x as x approaches 0 and the implications of continuity. There is no consensus on whether 1/0 can be defined as infinity.

Contextual Notes

Limitations include the undefined nature of the function at x=0, the differing left and right limits, and the implications of continuity that are not universally accepted in this context.

NotASmurf
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lim 1/x as x->0 is infinity, but the function taking it to infinity is continuous, but for continuous functions f(a)= lim f(x) as x->a, so by defininition 1/0 is infinity, what is wrong with this logic?
 
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1/x is not defined at x=0. This means that ##f(a)## does not exist, hence you can't appeal to continuity (continuity requires a function to be defined there).
 
a is 0, f=1/x
 
NotASmurf said:
a is 0, f=1/x
Yeah, sorry. I realized and edited my post. You replied just before I finished.
 
oh, 1/x, x element of R, and inf not element of R but cardinality, thanks.
 
Also, I want to point out
lim 1/x as x->0 is infinity
is not true. The left and right limits are not the same.
 
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pwsnafu said:
Also, I want to point out

is not true. The left and right limits are not the same.

Why not? 1/x coming from the negative side to 0 should yield same result as from the positive?
 
NotASmurf said:
Why not? 1/x coming from the negative side to 0 should yield same result as from the positive?
No.The limit from the left is ##-\infty##. For example ##1/(-.01) = -100##
 
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NotASmurf said:
but for continuous functions f(a)= lim f(x) as x->a
There is no way to extend the definition of f to x=0 in a continuous way.
 
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NotASmurf said:
lim 1/x as x->0 is infinity, but the function taking it to infinity is continuous, but for continuous functions f(a)= lim f(x) as x->a, so by defininition 1/0 is infinity, what is wrong with this logic?
Take a look at the graph of y = 1/x. There is the worst possible kind of discontinuity at x = 0, with ##\lim_{x \to 0^-} \frac 1 x = -\infty## and ##\lim_{x \to 0^+} \frac 1 x = +\infty##.
 

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