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Mathematics 17 Online
OpenStudy (steve816):

Limit question.

OpenStudy (steve816):

How do I solve this algebraically?\[\lim_{x \rightarrow \infty}\frac{ \ln x^2 }{ \ln x }\]

OpenStudy (yagosik):

Well, you can use this formula for a tip: \[\ln(a*b)=\ln(a)+\ln(b)\]

OpenStudy (sweetburger):

Use Lhops. Differentiate the numerator and then differentiate the denominator. you get something like this \[\lim_{x \rightarrow \infty }\frac{ \frac{ 2 }{ x } }{ \frac{ 1 }{ x } } =\]

OpenStudy (sweetburger):

Do you follow what I did?

OpenStudy (steve816):

Umm, I do not know what Lhops are. Can you show me how you got those values please?

OpenStudy (sweetburger):

Sure. The numerator is ln(x^2). Rewrite ln(x^2) as 2ln(x). The derivative of 2ln(x) = 2/x. This becomes the numerator. The denominator is ln(x). The derivative of ln(x) is 1/x. This becomes the denominator. lhops is short for l'hopital's rule

OpenStudy (sweetburger):

You could also simply look at it like this if that is confusing you. \[\ln(x^2) = 2\ln(x)\] \[\lim_{x \rightarrow \infty } \frac{ 2\ln(x) }{ \ln(x) }\] Do you notice that there is both a ln(x) in the numerator in the denominator?

OpenStudy (steve816):

Ohh thank you sweetburger.

OpenStudy (steve816):

It is much more clear now!

OpenStudy (sweetburger):

You can cancel out the ln(x) in both the numerator and the denominator to get \[\lim_{x \rightarrow \infty } 2 = \frac{ 2\ln(x) }{ \ln(x)} = 2\]

OpenStudy (sweetburger):

Either way you arrive at the same answer which is 2.

OpenStudy (steve816):

Got it thanks!

OpenStudy (sweetburger):

Alright np :)

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