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Mathematics 8 Online
OpenStudy (anonymous):

Trouble with another limit..

OpenStudy (anonymous):

It is \[\lim_{x \rightarrow 0} \left( 1 + 3x \right)^{2+\frac{ 1 }{ 4x ^{2}}}\]

OpenStudy (anonymous):

Answer is \[e ^{\frac{ 3 }{ 4 }}\], just dont know how to get there.

OpenStudy (anonymous):

Really having touble with the \[\lim_{x \rightarrow 0} \frac{ \ln \left( 1 + 3x \right) }{\frac{ 1 }{ 2 + \frac{ 1 }{ 4x ^{2} } } }\] bit.

OpenStudy (anonymous):

More Specifically, \[\frac{ d }{ dx } {\frac{ 1 }{ 2 + \frac{ 1 }{ 4x ^{2} } } } \]

OpenStudy (anonymous):

the \[4x^{2}\] should just be a 4x.

OpenStudy (anonymous):

do you know the answer to this problem?\[\lim_{n\rightarrow \infty}\left(1+\frac{3}{n}\right)^n\] Because a substitution of:\[x=\frac{1}{n}\]and noticing that\[x\rightarrow 0 \iff n\rightarrow \infty\] can change this problem into the first equation (with some extra baggage that can be taken care of on the side).

OpenStudy (anonymous):

Answer would just be e^3 right? Clever, will give original a shot this way.

OpenStudy (anonymous):

Just saw another condition, cant use L'Hoptials. This sucks.

OpenStudy (experimentx):

The limit goes to infinity for your expression. if your expression is \[ \lim_{x\to 0} (1 + 3x^2)^{\frac 1 {4x^2}}\] then your limit is \( e^{3/4}\). Just use the definition of \( e\) as hinted by Joemath

OpenStudy (experimentx):

Woops!! two different values, http://www.wolframalpha.com/input/?i=limit+x-%3E0+%281%2B3*x%29^%282+%2B+1%2F%284*x^2%29%29 limit x->0- goes to 0 because, |1-3x| <1 while x->0+ goes to infinity because you would encounter something like e^(3/4 * 1/x)

OpenStudy (anonymous):

Thanks experimentX, I'd made a mistake typing the above. Actually looks like this. limit x->0 (1+3*x)^(2 + 1/(4*x))

OpenStudy (anonymous):

Well here's how wolfram does it.

OpenStudy (experimentx):

yes, one way to deal it with is to use the definition of e. remove the square first, it evaluates to 1, the second term (1+3/x)^(4/x) is (1+3/x)^(3/x* 4/3) which is e^(4/3)

OpenStudy (anonymous):

Awesome, thank you :) - wolframs way seems a bit long winded.

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