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Mathematics 10 Online
OpenStudy (anonymous):

help finding sum of series

OpenStudy (anonymous):

OpenStudy (anonymous):

its supposed to match ar^(n-1)

OpenStudy (solomonzelman):

one question, will the sum be exact or approximate ?

OpenStudy (anonymous):

its 12

OpenStudy (solomonzelman):

-:( the number of terms is ∞

OpenStudy (agreene):

what type of series is this drbgonzal ? that will help you figure out how to approach it.

OpenStudy (anonymous):

yeah but you find where they converge

OpenStudy (anonymous):

OpenStudy (agreene):

Right, the answer is 12 and the series converges on that value. Are you needing help on knowing why? or just wanted to check your answers?

OpenStudy (anonymous):

i need to know why

OpenStudy (agreene):

So, do you know what type of series this is?

OpenStudy (agreene):

like alternating, or geometric or taylor series?

OpenStudy (anonymous):

it says infinite series

OpenStudy (agreene):

Yes, it is. But there are different types, so in this case it is a geometric series (you perhaps havent heard of the others)

OpenStudy (anonymous):

ive heard of some of them but i included ar^(n-1) but didn't know what to call it because of n+1

OpenStudy (agreene):

geometric series are structured like this: \[\sum_{n=1}^{\infty}ar^n=a+ar+ar^2+ar^3...ar^n+ar^{n+1}\] and converges if \(|r|<1\) then it converges to \[\frac{a}{1-r}\] in this case: \[\sum_{n=0}^{\infty}\frac{4^{n+1}}{6^n}=-4*3^{-m} (2^{m+1}-3^{m+1})\] So:it converges and it does it at 12

OpenStudy (anonymous):

thnx

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