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Mathematics 8 Online
OpenStudy (anonymous):

@Michele_Laino

OpenStudy (michele_laino):

hint: evaluate this limit, please: \[\lim _{x \rightarrow \infty}\frac{ e ^{x+3} }{ e ^{x} }=...\]

OpenStudy (michele_laino):

another hint: please note that: \[\frac{ e ^{x+3} }{ e ^{x} }=e ^{3}\] so?

OpenStudy (anonymous):

it is B!

OpenStudy (michele_laino):

no, because: \[\lim _{x \rightarrow +\infty}\frac{ e ^{3x} }{ e ^{x} }=\lim _{x \rightarrow +\infty}e ^{2x}=+\infty\]

OpenStudy (anonymous):

oh so it is C?

OpenStudy (michele_laino):

no, because: \[\lim _{x \rightarrow +\infty}\frac{ e ^{2x} }{ e ^{x} }=\lim _{x \rightarrow + \infty}e ^{x}=+\infty\]

OpenStudy (michele_laino):

yes!, because: \[\lim _{x \rightarrow +\infty}\frac{ e ^{x+3} }{ e ^{x} }=e ^{3}\neq 0\]

OpenStudy (michele_laino):

hint: \[\frac{ x+sinx }{ x }=1+\frac{ \sin x }{ x }\] so?

OpenStudy (anonymous):

they are the same rate!

OpenStudy (michele_laino):

yes, because if x>0, since x---> +infinity, we have: \[-\frac{ 1 }{ x }\le \frac{ \sin x }{ x }\le \frac{ 1 }{ x }\] since: \[-\frac{ 1 }{ x }\rightarrow 0, \frac{ 1 }{ x }\rightarrow 0\] when x--->+infty, we have: \[\lim _{x \rightarrow +\infty}\frac{ \sin x }{ x }=0\] and: \[\lim _{x \rightarrow +\infty}\left( \frac{ x+ \sin x }{ x } \right)=0\]

OpenStudy (michele_laino):

of course, the same result we will get in the case x--->-infinity

OpenStudy (michele_laino):

namely: \[x \rightarrow -\infty\]

OpenStudy (anonymous):

so it is C (:

OpenStudy (michele_laino):

oops... \[\lim _{x \rightarrow +\infty}\left( \frac{ x+ \sin x }{ x } \right)=1\]

OpenStudy (anonymous):

wait is it c?

OpenStudy (michele_laino):

yes! it is C

OpenStudy (anonymous):

thank you !!!!

OpenStudy (michele_laino):

thank you! :)

OpenStudy (anonymous):

thank you !!!!

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