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Mathematics 17 Online
OpenStudy (luigi0210):

Does this sequence diverge or converge?

OpenStudy (luigi0210):

\[\LARGE a_{n}=(1+\frac{2}{n})^n\]

OpenStudy (anonymous):

Converges to e^2

OpenStudy (luigi0210):

Could you explain how you got that? I'm new to learning this stuff :P

ganeshie8 (ganeshie8):

substitute n = 2x, \(\LARGE a_{x}=(1+\frac{1}{x})^{2x} = \left((1+\frac{1}{x})^{x}\right)^2 \)

ganeshie8 (ganeshie8):

take the limit as x goes to infinity

OpenStudy (luigi0210):

Thank you guys :)

ganeshie8 (ganeshie8):

np :) we use the known limit \(\large \lim \limits_{x \to \infty} \left(1 + \frac{1}{x}\right)^x = e\)

ganeshie8 (ganeshie8):

the sequence converges if the limit \(\lim \limits_{n \to \infty }a_n\) exists

OpenStudy (luigi0210):

And since it got reduced to \[\Large \lim_{x \rightarrow \infty} (e)^2\] it just became \(\Large e^2\) right?

ganeshie8 (ganeshie8):

yes ! but it is illegal to show limit notation after taking the limit..

ganeshie8 (ganeshie8):

\[\large \lim \limits_{x\to \infty }a_{x}= \lim \limits_{x \to \infty } \left((1+\frac{1}{x})^{x}\right)^2\] \[\large =\left( \lim \limits_{x \to \infty } (1+\frac{1}{x})^{x}\right)^2\] \[\large =\left( e\right)^2\]

ganeshie8 (ganeshie8):

in the third step limit notation should not be present as the limit was already taken ^

OpenStudy (luigi0210):

Oh, alright, thanks for the clarification gane :)

ganeshie8 (ganeshie8):

np :)

OpenStudy (dan815):

boootifful

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