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Mathematics 8 Online
OpenStudy (anonymous):

Find

OpenStudy (anonymous):

OpenStudy (anonymous):

2,054 2,119 2,142 2,212

OpenStudy (anonymous):

i got 2212 am i correct?@mathmate

OpenStudy (anonymous):

@mathmate

OpenStudy (mathmate):

Yes, 2212 is correct. Did you apply the same formula? Hope you did not calculate all 14 terms and added them up!

OpenStudy (anonymous):

1 more question

OpenStudy (anonymous):

Find the 6th partial sum of

OpenStudy (anonymous):

OpenStudy (anonymous):

78,432 11,204 9,555 2,387

OpenStudy (anonymous):

don't know how to do this one

OpenStudy (mathmate):

Do you know the formula for sum of geometric series?

OpenStudy (anonymous):

is it Sn=(a1-a1r^n)/(1-r)

OpenStudy (mathmate):

Yes, or same as \(Sn=a1(1-r^n)/(1-r)\)

OpenStudy (mathmate):

What is your a1?

OpenStudy (anonymous):

7

OpenStudy (mathmate):

r=?

OpenStudy (anonymous):

4

OpenStudy (mathmate):

So substitute in formula and see what you get...

OpenStudy (anonymous):

wats n?

OpenStudy (mathmate):

You're calculating S13, so n=13.

OpenStudy (anonymous):

how did u get 13?im confused

OpenStudy (mathmate):

Sn=a1(1−r^n)/(1−r) n stands for the nth partial sum. Oh, 6th partial sum, so n=6! sorry! :(

OpenStudy (anonymous):

ok

OpenStudy (mathmate):

What do you get?

OpenStudy (anonymous):

just a sec

OpenStudy (anonymous):

got 9555

OpenStudy (anonymous):

thnx

OpenStudy (mathmate):

9555 is correct! Congrats again! :)

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