What is the limit of lnx as x approaches a negative number?

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Homework Help Overview

The discussion revolves around the limit of the natural logarithm function, specifically as the variable approaches a negative number. Participants are exploring the implications of the logarithm's domain and behavior near zero.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants question the applicability of L'Hôpital's rule and express uncertainty about how to approach the limit. There is a focus on understanding the behavior of ln(x) as x approaches zero and negative values, with some participants referencing known limits and their implications.

Discussion Status

There is an ongoing exploration of the limits involved, with some participants asserting that the limit does not exist for negative inputs. Others are attempting to clarify the nature of infinity in the context of the logarithm's limits and questioning the setup of the original problem.

Contextual Notes

Participants note that ln(x) is undefined for negative numbers, which raises questions about the original problem statement and its validity. There is mention of right-handed limits and potential misunderstandings in the problem's formulation.

Nipuna Weerasekara
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Homework Statement


Find the following limit.

Homework Equations


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The Attempt at a Solution



I cannot apply L' Hopital rule because it does not apply to this question. Hence I have no idea how to approach to this question. Please give me some guidelines.
 
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What is lim(x->0) lnx? What is lim(x->0) 1/x^n?
 
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Math_QED said:
What is lim(x->0) lnx? What is lim(x->0) 1/x^n?
I already know the answer to this and it is zero but I do not know how it comes.
For your question, lim (x->0) lnx is infinity and lim(x->0) 1/x^n is again infinity.
But I do not find any help from these two.
 
Nipuna Weerasekara said:
I already know the answer to this and it is zero but I do not know how it comes.
For your question, lim (x->0) lnx is infinity and lim(x->0) 1/x^n is again infinity.
But I do not find any help from these two.

The answer is not zero.
And more specifically, what kind of infinity are the limits above I asked for? I also forgot to mention the following very important thing: lim(x->0) lnx is NOT defined. The right handed limit is defined though.
 
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Math_QED said:
The answer is not zero.
And more specifically, what kind of infinity are the limits above I asked for? I also forgot to mention the following very important thing: lim(x->0) lnx is NOT defined. The right handed limit is defined though.
I think The question has some printing mistake or so. However thanks for your kind concern.
 
Nipuna Weerasekara said:
I think The question has some printing mistake or so. However thanks for your kind concern.

The answer is that the limit does not exist since lnx is undefined for negative numbers. The right handed limit can be obtained by splitting the limit in 2 separate limits by using lim x>a fg = (lim x>a f )*( lim x>a g).
 
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