Is h(x) Continuous at x=5 Given Conditions on f(x) and g(x)?

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    Continuity
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Discussion Overview

The discussion revolves around the continuity of the function h(x) at the point x=5, given the continuity of two other functions, f(x) and g(x), at the same point. The context includes mathematical reasoning and definitions related to continuity.

Discussion Character

  • Mathematical reasoning
  • Technical explanation
  • Homework-related

Main Points Raised

  • One participant asks for help in proving that h(x) is continuous at x=5, given that f(x) and g(x) are continuous at that point and both equal 8 at x=5.
  • Another participant suggests that the problem can be approached using the definition of continuity and that the limit of h(x) as x approaches 5 should equal 8, considering the two cases based on the definition of h(x).
  • A different participant recommends using the δ and ε method to write out the definitions of continuity for f(x), g(x), and h(x).
  • One participant expresses doubt about the necessity of the ε-δ method, proposing that one-sided limits might suffice for the proof.
  • There are questions raised about whether 5 is an accumulation point, with one participant asserting that since the function is continuous at that point, it is indeed an accumulation point of the image of h.
  • Another participant challenges the implication that all functions are continuous over isolated points, suggesting that this reasoning may be incorrect.

Areas of Agreement / Disagreement

Participants express differing views on the methods required to prove continuity, with some advocating for the ε-δ approach while others suggest one-sided limits are sufficient. There is also disagreement regarding the status of 5 as an accumulation point and its implications for continuity.

Contextual Notes

Some participants reference specific mathematical definitions and methods, but there is no consensus on the best approach to prove the continuity of h(x) at x=5. The discussion includes unresolved questions about the nature of accumulation points and their relevance to the problem.

blackisback
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Can anyone help me with this problem?

Say f(x) & g(x) are cont. at x=5.
Also that f(5)=g(5)=8.

If h(x)=f(x) when x<=5
and
h(x)=g(x) when x>=5:

prove h(x) is cont at x=5.
 
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Hmm, this appears to be a straightforward application of the definition of continuity at a point. You already know the h(5) exists, now you just need to show that the limit as x approaches 5 of h(x) is 8. This can be done as 2 particular cases, as h(x) either =f(x) or g(x), depending on which side you approach the point from.
 
Welcome to PF!

blackisback said:
Can anyone help me with this problem?

Say f(x) & g(x) are cont. at x=5.
Also that f(5)=g(5)=8.

If h(x)=f(x) when x<=5
and
h(x)=g(x) when x>=5:

prove h(x) is cont at x=5.

Hi blackisback ! Welcome to PF! :smile:

Just write out the definitions of:

f(x) is continuous at x = 5
g(x) is continuous at x = 5
h(x) is continuous at x = 5

using the δ and ε method.

Then just chug away. :smile:
 
thanks a lot guys
 
I don't think you need to use "epsilon-delta". Just using the one-sided limits should be enough.
 
Is 5 an accumulation point, ?
 
peos69 said:
Is 5 an accumulation point, ?

Since the function is continuous there, 5 is an accumulation point of the image of h under the standard topology inherited from R.
 
Since all functions are continuous over an isolated point in there domain your implication is incorrect
 

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