Another Limit, without L'hospital rule

  • MHB
  • Thread starter Chipset3600
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In summary, the conversation discusses solving a limit problem using substitution and a fundamental limit. The solution involves setting $x-2=y$ and $z=y\ \ln 5$, and using the fact that $5^y = e^{y\ \ln 5}$. The final result is 25ln(5).
  • #1
Chipset3600
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Hello MHB, i can't hv success with this limit, help me please:
[TEX]\lim_{x->2}\frac{5^{x}-25}{x-2}[/TEX]
 
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  • #2
Chipset3600 said:
Hello MHB, i can't hv success with this limit, help me please:
[TEX]\lim_{x->2}\frac{5^{x}-25}{x-2}[/TEX]

Setting $x-2=y$ You obtain...

$\displaystyle \frac{5^{x}-25}{x-2} = \frac{5^{2+y}-5^{2}}{y}= 5^{2}\ \frac{5^{y}-1}{y} = 5^{2}\ \ln 5\ \frac{e^{y\ \ln 5} -1} {y\ \ln 5}$ (1)

and setting $z= y\ \ln 5$ You arrive at the limit...

$\displaystyle \lim_{z \rightarrow 0} 5^{2}\ \ln 5\ \frac{e^{z}-1}{z}$ (2)

... who contains a 'fundamental limit'...

Kind regards

$\chi$ $\sigma$
 
  • #3
chisigma said:
Setting $x-2=y$ You obtain...

$\displaystyle \frac{5^{x}-25}{x-2} = \frac{5^{2+y}-5^{2}}{y}= 5^{2}\ \frac{5^{y}-1}{y} = 5^{2}\ \ln 5\ \frac{e^{y\ \ln 5} -1} {y\ \ln 5}$ (1)

and setting $z= y\ \ln 5$ You arrive at the limit...

$\displaystyle \lim_{z \rightarrow 0} 5^{2}\ \ln 5\ \frac{e^{z}-1}{z}$ (2)

... who contains a 'fundamental limit'...

Kind regards

$\chi$ $\sigma$

I can't understood ur z=yln(5)
 
  • #4
Chipset3600 said:
I can't understood ur z=yln(5)

Simply You set $y\ \ln 5 = z$ and then insert z in (1)...

Kind regards

$\chi$ $\sigma$
 
  • #5
chisigma said:
Simply You set $y\ \ln 5 = z$ and then insert z in (1)...

Kind regards

$\chi$ $\sigma$

where it came from this ln(5)?
 
  • #6
Chipset3600 said:
where it came from this ln(5)?

Is $\displaystyle 5^{y}= e^{y\ \ln 5}$...

Kind regards

$\chi$ $\sigma$
 
  • #7
chisigma said:
Is $\displaystyle 5^{y}= e^{y\ \ln 5}$...

Kind regards

$\chi$ $\sigma$

Now i understood, nd i find the result 25ln(5). Thank you :)
 

FAQ: Another Limit, without L'hospital rule

What is "Another Limit, without L'hospital rule"?

"Another Limit, without L'hospital rule" is a mathematical concept used to find the limit of a function without using the L'Hospital's rule. This technique involves simplifying the function algebraically and using other limit laws to find the answer.

Why is it important to learn how to find limits without L'hospital rule?

Learning how to find limits without L'hospital rule allows for a better understanding of mathematical concepts and principles. It also helps in solving more complex problems and in developing critical thinking skills.

What are the steps to find a limit without using L'hospital rule?

The steps to find a limit without using L'hospital rule are as follows:

  1. Simplify the function algebraically.
  2. Factor if possible.
  3. Apply limit laws, such as the sum, difference, product, and quotient laws.
  4. If necessary, use other techniques, such as substitution or factoring to simplify the function further.
  5. Once the function is simplified, plug in the value of the limit to find the answer.

Can L'hospital rule be used in all limit problems?

No, L'hospital rule can only be used in certain types of limit problems, such as indeterminate forms (e.g. 0/0 or ∞/∞). It cannot be used if the limit is not in the form of an indeterminate form.

Are there any disadvantages to using L'hospital rule in finding limits?

While L'hospital rule can be a helpful tool in finding limits, it may not always give the correct answer or may be difficult to apply in certain situations. It is important to understand other methods, such as finding limits without L'hospital rule, to verify the answer or to use when L'hospital rule cannot be applied.

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