Mathematics OpenStudy (anonymous):

what formula do I use for What is the sum of an 8–term geometric series if the first term is –11, the last term is 180,224, and the common ratio is –4?? OpenStudy (anonymous):

-11 x -4 = ? x -4 = ? x -4 = ? x -4 = ? x -4 = ? x -4 = ? x -4 = ? x -4 = 180,224 OpenStudy (anonymous):

Thanks but that isnt in my answer choices OpenStudy (anonymous):

but do you understand the reasoning? 8 times multiplying by -4. What are you answers? OpenStudy (anonymous):

no, I just need a formula, thats all OpenStudy (anonymous):

Look at this. Let's call \(S\) the sum of the first \(n\) terms with first term \(a_1\) and common ratio \(C\). \[\huge S=a_1+Ca_1+C^2a_1+\cdots+C^{n-1}a_1\]Let us now multiply both sides by \(C\).\[\huge CS=Ca_1+C^2a_1+C^3a_1 +\cdots+C^{n}a_1\]Now, we will subtract the second equation from the first. All but two terms cancel, no matter how many terms we began with.\[\huge S-CS=a_1-C^na_1=(1-C^n)a_1\]This implies the following, if we solve for \(S\).\[\huge \boxed{S=\dfrac{1-C^n}{1-C}\ a_1}\]

Latest Questions kinkajayplayz: found like an apple deep like a cup yet all the kings horses cannot pull it up!
8 seconds ago 0 Replies 0 Medals 88125574lovesah: Explain the phrases "weary of the 'Evil Question"' and "'sick of carpet-bag' gove
1 minute ago 0 Replies 0 Medals kinkajayplayz: A hill full a whole full but cannot catch a bowl full
1 minute ago 7 Replies 1 Medal meganagirre713: Why were reforms needed?
4 minutes ago 1 Reply 0 Medals kinkajayplayz: what has four legs in the morning two in the afternoon and three at night?
6 minutes ago 2 Replies 2 Medals jayleserodriguez: Rene would like to explore a career that would allow her to work with customers or clients.
9 minutes ago 0 Replies 0 Medals iosangel: https://prnt.sc/uqpv6q wat would be the angle measure for angle 10 and 9
10 minutes ago 0 Replies 0 Medals kinkajayplayz: long legs bandy thighs lil head and no eyes what am i?
7 minutes ago 16 Replies 2 Medals meganagirre713: Why does a coastal area have less variation in temperature than a noncoastal area? Temperatures feel cool all year round due to the duration of daylight.
13 minutes ago 0 Replies 0 Medals meganagirre713: Habitat change occurs more frequently through natural causes than human activity. Please select the best answer from the choices provided T F
14 minutes ago 2 Replies 0 Medals