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Evaluate the following limit. Use l'Hôpital's Rule when it is convenient and applicable.

[tex]\[
\lim _{x \rightarrow 1} \frac{\ln x}{11x - x^2 - 10}
\][/tex]

Use l'Hôpital's Rule to rewrite the given limit so that it is not an indeterminate form.

[tex]\[
\lim _{x \rightarrow 1} \frac{\ln x}{11x - x^2 - 10} = \lim _{x \rightarrow 1}(\square)
\][/tex]


Sagot :

To evaluate the limit
[tex]$ \lim_{x \rightarrow 1} \frac{\ln(x)}{11x - x^2 - 10}, $[/tex]
we can start by checking if this limit is in an indeterminate form of the type [tex]\(\frac{0}{0}\)[/tex] or [tex]\(\frac{\infty}{\infty}\)[/tex].

First, substitute [tex]\(x = 1\)[/tex] into the numerator and the denominator:

- The numerator [tex]\(\ln(1) = 0\)[/tex].
- The denominator [tex]\(11 \cdot 1 - 1^2 - 10 = 11 - 1 - 10 = 0\)[/tex].

Since both the numerator and the denominator are zero, we have an indeterminate form [tex]\(\frac{0}{0}\)[/tex].

In this case, l'Hôpital's Rule is applicable, which states that for limits of the form [tex]\(\frac{0}{0}\)[/tex] or [tex]\(\frac{\infty}{\infty}\)[/tex], we can take the derivatives of the numerator and the denominator:

[tex]$ \lim_{x \rightarrow 1} \frac{\ln(x)}{11x - x^2 - 10} = \lim_{x \rightarrow 1} \frac{\frac{d}{dx}[\ln(x)]}{\frac{d}{dx}[11x - x^2 - 10]}. $[/tex]

Now, calculate the derivatives of the numerator and the denominator:

- The derivative of the numerator [tex]\(\ln(x)\)[/tex] is [tex]\(\frac{1}{x}\)[/tex].
- The derivative of the denominator [tex]\(11x - x^2 - 10\)[/tex] is [tex]\(11 - 2x\)[/tex].

Thus, applying l'Hôpital's Rule, we get:

[tex]$ \lim_{x \rightarrow 1} \frac{\ln(x)}{11x - x^2 - 10} = \lim_{x \rightarrow 1} \frac{\frac{1}{x}}{11 - 2x}. $[/tex]

Now, simplify the expression inside the limit:

[tex]$ \lim_{x \rightarrow 1} \frac{\frac{1}{x}}{11 - 2x} = \lim_{x \rightarrow 1} \frac{1}{x(11 - 2x)}. $[/tex]

Substitute [tex]\(x = 1\)[/tex] into this simplified expression:

[tex]$ \frac{1}{1 \cdot (11 - 2 \cdot 1)} = \frac{1}{11 - 2} = \frac{1}{9}. $[/tex]

Therefore, the limit is:

[tex]$ \boxed{\frac{1}{9}}. $[/tex]