Is the function continuous at x=2 in f(x)= (x^2-4)/(x-2)?

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Discussion Overview

The discussion revolves around the conditions necessary for a function to be continuous at a specific point, particularly focusing on the function f(x) = (x^2 - 4)/(x - 2) and its continuity at x = 2. The scope includes conceptual understanding of continuity, properties of limits, and examples illustrating discontinuities.

Discussion Character

  • Conceptual clarification
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant questions the necessary conditions for continuity at a point, suggesting that the right-hand and left-hand limits must exist and be equal.
  • Another participant clarifies that for continuity at a point c, three conditions must be met: f(c) must exist, the limit of f(x) as x approaches c must exist, and this limit must equal f(c).
  • A different viewpoint states that while differentiability implies continuity, the reverse is not true, using the example of a corner to illustrate a continuous function that is not differentiable.
  • An example is provided where a function has both left and right limits equal at a point but is not continuous due to the function not being defined at that point, termed a "removable discontinuity."
  • The specific function f(x) = (x^2 - 4)/(x - 2) is posed as a question regarding its continuity at x = 2.

Areas of Agreement / Disagreement

Participants express differing views on the necessary conditions for continuity, with some emphasizing the importance of limits and others focusing on the definition of the function at the point in question. The discussion remains unresolved regarding the continuity of the specific function at x = 2.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about the definitions of continuity and the nature of the function at x = 2. The mathematical steps leading to conclusions about continuity are not fully explored.

klmdad
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My Question is what 3 things are necessary for a function to be continuous at c?
I have Right hand must exist, left hand must exist
and right and left hands must be equal. I was told that this is worng.
 
Last edited:
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f(c) must exist

limit of f(x) as x approaches c must exist

limit of f(x) as x approaches c must equal f(c)


you were confusing continuity with the properties of one-sided limits that states if the right hand limit equals the left hand limit, then the limit as a whole exsists.
 
Last edited:
A function that is differentiable is always continuous
A function that is continouos is not always differentiable

Therefore, your left and right hands notion is wrong. Think about the corner. It is cts but not diffble.
 
If f(x)= x for x< 0
and f(x)= x for x> 0

Then both left and right sided limits exist and are both 0, of course, but f is not continuous at x= 0 because f(0) is not defined at x= 0.

That's called a "removable discontinuity" because you can make the function continuous just by defining f(0) to be 0, but then you have a different function.

Exercise: Is f(x)= (x2- 4)/(x- 2) continuous at x= 2?
 
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