Indeterminate Products Giving Me Two Different Limits

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In summary, the question is about finding the limit as x approaches 0 for x times the natural logarithm of x. The two attempts at solving the problem involve using the quotient rule and the chain rule, but ultimately result in different answers due to a mistake in the second attempt.
  • #1
moe darklight
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Homework Statement



lim x-->0 of [tex]x lnx[/tex]

Homework Equations


The Attempt at a Solution



1) [tex]\frac{lnx}{1/x}[/tex] = [tex]\frac{1/x}{-1/x^{2}}[/tex] = (-x) = 0

2) [tex]\frac{x}{1/lnx}[/tex] = [tex]\frac{1}{1/1/x}[/tex] = [tex]\frac{1}{x}[/tex] = [tex]\infty[/tex]
 
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  • #2
hmmm...are you sure [tex]\frac{d}{dx} \frac{1}{\ln (x)}=\frac{1}{\frac{1}{x}}[/tex]?:wink:
 
  • #3
yea I realized it after a minute of looking at it again. this is exactly the sort of stupid mistake that lowers my marks in tests.

and oops. I didn't see you answer or I wouldn't have edited the entry back.

edit edit: there, I put it back up... but for some reason I think I made a double of the thread... agh. it's 4 AM. I'm tired :rofl:

edit edit edit: and, of course: thanks.

(I go sleep now)
 
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1. What is an indeterminate product?

An indeterminate product is a mathematical expression in which one or more factors approach zero or infinity, resulting in a limit that is undefined or indeterminate.

2. How do I determine the limit of an indeterminate product?

The limit of an indeterminate product can be determined by using algebraic manipulation or applying L'Hopital's rule, which involves taking the derivative of both the numerator and denominator and then evaluating the limit again.

3. Can an indeterminate product give me two different limits?

Yes, an indeterminate product can give you two different limits. This occurs when the factors in the expression approach different values as the limit is evaluated.

4. Why are indeterminate products important?

Indeterminate products are important because they represent situations in which traditional methods of finding limits may not be applicable. They also arise frequently in calculus and other areas of mathematics.

5. How can I avoid making mistakes when evaluating indeterminate products?

To avoid making mistakes when evaluating indeterminate products, it is important to carefully factor and simplify the expression before attempting to find the limit. It is also helpful to double-check your work and apply L'Hopital's rule if necessary.

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