Solving Limit Using L'Hospital's Rule

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In summary, When evaluating the limit (lim.t\rightarrow0) \frac{e^6^t-1}{t} using l'Hôpital's rule, you need to take the derivative of the top and bottom separately. Using the difference quotient rule will result in an indeterminate form, but taking the derivatives separately will give a non-indeterminate form and allow you to find the limit. In this case, the limit is 6.
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Homework Statement


evaluate the limit
[tex] (lim.t\rightarrow0) \frac{e^6^t-1}{t} [/tex]


Homework Equations


l'hospital's rule i guess


The Attempt at a Solution


With the usual approach of this rule, you are suppose to take a derivative and evaluate the derivative at that original limit. The problem is that every time I take a derivative and apply the limit I keep getting an indeterminate form. I don't know how to solve this. Can someone point me in the right direction?

Thanks
 
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  • #2
Once you use l'Hôpital's rule once, it's not in an indeterminate form and you can find the limit. Try showing your work.
 
  • #3
ok so

[tex] \frac {d}{dx} (\frac {e^6^t-1}{t})

= \frac{t(6e^6^t)-(e^6^t-1)}{t^2}

= \frac {6te^6^t-e^6^t+1}{t^2}[/tex]

apply the limit

[tex] \frac{0-1+1}{0}= \frac {0}{0} [/tex]
 
  • #4
When using l'Hôpital's rule, you take the derivative of the top and bottom separately, do not use the difference [STRIKE]quotient[/STRIKE] rule!
[tex]\lim_{x\rightarrow 0}\frac{f(x)}{g(x)} = \lim_{x\rightarrow 0}\frac{f'(x)}{g'(x)}[/tex]
 
Last edited:
  • #5
oh so NO quotient rule? oh ok. let me redo it then hold on.
 
  • #6
well just looking at it the answer is 6. wow thanks for that. I thought you had to use the quotient rule.

many thanks
 

1. What is L'Hospital's Rule?

L'Hospital's Rule is a mathematical tool used to evaluate limits of functions that are in an indeterminate form, such as 0/0 or ∞/∞. It states that if the limit of the ratio of two functions is in an indeterminate form, then the limit of the ratio of their derivatives will be the same. This rule was discovered by French mathematician Guillaume de l'Hôpital in the 17th century.

2. When should L'Hospital's Rule be used?

L'Hospital's Rule should only be used when the limit of a function is in an indeterminate form. This means that when plugging in the given value for x, the numerator and denominator both result in either 0 or ∞. If the limit is not in an indeterminate form, L'Hospital's Rule is not necessary and the limit can be evaluated using other methods.

3. How do you use L'Hospital's Rule?

To use L'Hospital's Rule, you must first check if the limit is in an indeterminate form. If it is, take the derivative of both the numerator and denominator and then evaluate the new limit. If the new limit is still in an indeterminate form, repeat the process until the limit can be evaluated. If the limit is not in an indeterminate form after one or two applications of L'Hospital's Rule, it means that the original limit does not exist.

4. What are the limitations of L'Hospital's Rule?

One limitation of L'Hospital's Rule is that it can only be used for limits that are in indeterminate form. If the limit is not in an indeterminate form, L'Hospital's Rule cannot be applied. Additionally, L'Hospital's Rule cannot be used for limits involving exponentials or logarithms. In these cases, other methods such as algebraic manipulation or using trigonometric identities may be used.

5. Are there any alternative methods for solving limits besides L'Hospital's Rule?

Yes, there are several alternative methods for solving limits. Some common methods include algebraic manipulation, substitution, and using known limits and properties of limits. The method used will depend on the type of limit and the given function. It is important to be familiar with multiple methods in order to determine the best approach for solving a particular limit.

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