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Mathematics 18 Online
OpenStudy (anonymous):

I suck at these

OpenStudy (anonymous):

at what

OpenStudy (jdoe0001):

ice cream? me too, I like sucking them too

OpenStudy (anonymous):

lol

OpenStudy (anonymous):

I love ice cream

OpenStudy (anonymous):

come on guys focus

OpenStudy (anonymous):

one sec while I write it

OpenStudy (anonymous):

\[\sum_{i=1}^{infinity} 7(4)^{i-1}\]

OpenStudy (anonymous):

Find the 6th partial sum of

OpenStudy (jdoe0001):

one sec

OpenStudy (jdoe0001):

\(\large {\huge \Sigma}_{i=1}^{\infty}\quad a_1{\color{blue}{ r}}^{i-1}\implies a_1\left(\cfrac{1-{\color{blue}{ r}}^i}{i-{\color{blue}{ r}}}\right)\)_

OpenStudy (jdoe0001):

hmmm lemme fix that

OpenStudy (anonymous):

Ok

OpenStudy (jdoe0001):

\(\large {\huge \Sigma}_{i=1}^{\infty}\quad a_1{\color{blue}{ r}}^{i-1}\implies a_1\left(\cfrac{1-{\color{blue}{ r}}^i}{1-{\color{blue}{ r}}}\right)\)

OpenStudy (jdoe0001):

notice, you're asked for the "6th partial sum" thus \(\large \bf {\huge \Sigma}_{i=1}^{\infty}\quad 7{\color{blue}{ 4}}^{{\color{brown}{ i}}-1}\implies 7\left(\cfrac{1-{\color{blue}{ 4}}^{\color{brown}{ 6}}}{1-{\color{blue}{ 4}}}\right)\)

OpenStudy (anonymous):

alright

OpenStudy (jdoe0001):

hmmm I should separate the 7 and 4...so \(\Large \bf {\huge \Sigma}_{i=1}^{\infty}\quad 7{\color{blue}{ (4)}}^{{\color{brown}{ i}}-1}\implies 7\left(\cfrac{1-{\color{blue}{ 4}}^{\color{brown}{ 6}}}{1-{\color{blue}{ 4}}}\right)\)

OpenStudy (jdoe0001):

but anyhow... that's how you'd get the 6th partial sum

OpenStudy (anonymous):

so 7(85)?

OpenStudy (anonymous):

@jdoe0001

OpenStudy (jdoe0001):

hmmm not quite

OpenStudy (jdoe0001):

recall your PEMDAS :)

OpenStudy (anonymous):

ok what should I do?

OpenStudy (jdoe0001):

well... you'd do the subtractions in the fraction first then the multiplication, and then the division

OpenStudy (jdoe0001):

\(\bf 7\left(\cfrac{1-4^6}{1-4}\right)\implies \cfrac{7(1-4^6)}{1-4}\)

OpenStudy (anonymous):

595?

OpenStudy (jdoe0001):

hmmm.... check your operations...nope,, is a bigger value

OpenStudy (anonymous):

but the 6th root of -4 is -256

OpenStudy (anonymous):

oh wait its 256

OpenStudy (anonymous):

im so lost lol

OpenStudy (anonymous):

oh wait its 9555

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