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Mathematics 15 Online
OpenStudy (anonymous):

Limit question. Please help

OpenStudy (anonymous):

\[\lim_{x \rightarrow 0} = \frac{ 3^{1/x} - 1 }{ 3^{1/x} +1 }\]

myininaya (myininaya):

are you allowed to use l'hosptal?

OpenStudy (anonymous):

No I unfortunately am not allowed to

myininaya (myininaya):

ok let me think for a sec then on other ways

OpenStudy (anonymous):

Ok thanks

myininaya (myininaya):

ok and do you know how to differentiate 3^(1/x)?

OpenStudy (anonymous):

No I do not

myininaya (myininaya):

\[x>0 \text{ we have } 3^\frac{1}{x}-1>0 \\ x<0 \text{ we have } 3^\frac{1}{x}-1<0 \\ \text{ for any real } x \neq 0 \text{ we have } 3^\frac{1}{x}+1>0 \]

myininaya (myininaya):

This should help you to conclude something about the actual limit since this giving you information about the left and right limit.

myininaya (myininaya):

Like we don't need to know the exact left and right limit just that they differ.

OpenStudy (anonymous):

For this question I have to show all the work. How would I show that?

myininaya (myininaya):

Well I know 3^a is positive for any real a so 3^a+1 is still greater than 0

myininaya (myininaya):

3^a-1 if a=0 then we have 1-1 but if a<0 then 0<3^a<1 so 3^a-1 will be negative but if a>0 then 3^a>1 so 3^a-1 will be positive

myininaya (myininaya):

since the left and right limit differ then the actual limit doesn't exist

OpenStudy (anonymous):

Okay thanks

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