Limit Calculation Help: x^3(ln(x))^2

In summary, the limit of x^3(ln(x))^2 as x approaches infinity is infinity because the logarithmic term (ln(x))^2 increases without bound. L'Hopital's rule can be used to evaluate the limit, as well as the squeeze theorem. However, the limit of x^3(ln(x))^2 as x approaches 0 does not exist due to the negative logarithmic term. The expression cannot be simplified before evaluating the limit.
  • #1
Yankel
395
0
Hello

I need some help with this limit. I know I should use the L'hopital rule, but not sure how to do it...any help will be appreciated !

[tex]\lim_{x\to 0^{+}}x^{3}\cdot (ln(x))^{2}[/tex]
 
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  • #2
I notice this is the indeterminate form $0\cdot\infty$, so I would recommend writing it as:

$\displaystyle \lim_{x\to0^{+}}\frac{\ln^2(x)}{x^{-3}}$

Now we have the indeterminate form $\dfrac{\infty}{\infty}$ and we may apply L'Hôpital's rule.

Can you proceed?
 

FAQ: Limit Calculation Help: x^3(ln(x))^2

1. What is the limit of x^3(ln(x))^2 as x approaches infinity?

The limit of x^3(ln(x))^2 as x approaches infinity is infinity. This is because as x gets larger and larger, the logarithmic term (ln(x))^2 will also increase without bound, causing the overall expression to approach infinity.

2. Can the limit of x^3(ln(x))^2 be evaluated using L'Hopital's rule?

Yes, the limit of x^3(ln(x))^2 can be evaluated using L'Hopital's rule. Taking the derivative of the function results in 3x^2(ln(x))^2 + 2x^2ln(x), which still approaches infinity as x approaches infinity. Therefore, L'Hopital's rule can be applied again until the limit is determined.

3. What happens to the limit of x^3(ln(x))^2 as x approaches 0?

The limit of x^3(ln(x))^2 as x approaches 0 does not exist. This is because as x gets closer to 0, the logarithmic term (ln(x))^2 will become negative and cause the overall expression to approach negative infinity. However, if the limit is approached from the right side of 0, it will approach infinity.

4. Is it possible to simplify the expression x^3(ln(x))^2 before evaluating the limit?

No, it is not possible to simplify the expression x^3(ln(x))^2 before evaluating the limit. The logarithmic term cannot be simplified further and the power of x cannot be reduced without changing the overall expression.

5. Can the limit of x^3(ln(x))^2 be evaluated using the squeeze theorem?

Yes, the limit of x^3(ln(x))^2 can be evaluated using the squeeze theorem. By choosing two functions that are both greater than or equal to x^3(ln(x))^2 and have a limit of infinity as x approaches infinity, the squeeze theorem can be used to show that the limit of x^3(ln(x))^2 is also infinity.

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