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Mathematics 21 Online
OpenStudy (anonymous):

Calculus II question!

OpenStudy (anonymous):

OpenStudy (anonymous):

We have no idea where to start, any help? PLease File is attached.

OpenStudy (amistre64):

Start with subbing in the equation for Pn into Pn

OpenStudy (anonymous):

There is only one equation I got this. \[\sum_{n=0}^{\infty} (\frac{ \lambda }{ \mu })^n(1-\frac{ \lambda }{ \mu })\]

OpenStudy (amistre64):

\[\sum_{n=0}^{inf}r^n(1-r)=1\] \[\sum_{n=0}^{inf}r^n-r^{n-1}=1\] \[\sum_{n=0}^{inf}r^n-\sum_{n=0}^{inf}r^{n-1}=1\] \[\sum_{n=0}^{inf}r^n=1+\sum_{n=0}^{inf}r^{n-1}\] are some owrk abouts

OpenStudy (amistre64):

since 0<|r|<1 the series converge and we can sub in some formulas

OpenStudy (amistre64):

\[\sum_{n=0}^{inf}r^n-\sum_{n=0}^{inf}r^{n+1}=1\] \[\frac{1}{1-r}-r\frac{1}{1-r}=1\] \[\frac{1}{1-r}(1-r)=1\]

OpenStudy (amistre64):

n-1 was a typo .... :)

OpenStudy (amistre64):

since r is neither 1 nor 0 .... this is true for all r

OpenStudy (anonymous):

Wait, all you did was distribute the r^n in the second step, should it be plus and not minus?

OpenStudy (amistre64):

yeah, n+1 which i caught later ...

OpenStudy (anonymous):

Oh okay!

OpenStudy (anonymous):

And for the second part? how would we do that?

OpenStudy (amistre64):

same concept ....

OpenStudy (amistre64):

n (r^n(1-r) )

OpenStudy (amistre64):

of we can see this as a telescoping sum that reduces to this 0 +r - r^2 +2r^2 - 2r^3 +3r^3 - 3r^4 +4r^4 - 4r^5 +5r^5 - 5 r^6 ------------------------------------ r + r^2 + r^3 + r^4 + r^5 + .....

OpenStudy (amistre64):

in other words: that formulas out to:\[\frac{r}{1-r}\]

OpenStudy (amistre64):

do you understand where the formulas for an infinite geometric series come from?

OpenStudy (anonymous):

Thanks so much man!

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