At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident, similique sunt in culpa qui officia deserunt mollitia animi, id est laborum et dolorum fuga.
Et harum quidem rerum facilis est et expedita distinctio. Nam libero tempore, cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus, omnis voluptas assumenda est, omnis dolor repellendus.
Itaque earum rerum hic tenetur a sapiente delectus, ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat.

Get our expert's

answer on brainly

SEE EXPERT ANSWER

Get your **free** account and access **expert** answers to this and **thousands** of other questions.

See more answers at brainly.com

Get this expert

answer on brainly

SEE EXPERT ANSWER

Get your **free** account and access **expert** answers to this and **thousands** of other questions

the formula for sum of n terms is
Sn = a1 * (1 - r^n)
------
1 - r

http://www.mathsisfun.com/algebra/sequences-sums-geometric.html

But what do I plug in there to get the answers?

r = common ratio = second term / first term
a1 = first term
and n = number of terms

so for question 1
r = -16/8 = -2
a1 = 8
and n = 15

So would the answer for the first one be 87384?

8 * ( 1 - (-2)^15)
------------- = 87384
1 - (-2)

Oh yay! I got it right! Sorry I suck at math...

A GS can be written as a, ar , ar^2 , ar^3 .......

Whoa how do I do 7 root in my calculator??

Do it like this: r ^ (- 7)

No!

Bad me!

r ^ (1/7)

That's what you want, \[\Huge r^{\frac{1}{7}}\]

Haha okay gimme a minute to figure this out...

I got 39364 for number 2 is that right?

Okay okay how do i do the last two??

That's what I got for #2 as well.

So, you have \(a\) and \(r\), and you need \(n\) or \(r^n\).

Do you see how to get that?

uhhh.... no not really...so it would be -11 (1-(-4^n)/(1--4)?

General guideline: if you want something, solve for it.

wait so n is -11,246??

No, \(a\ r^n=-11,264\). So you divide both sides by \(a=11\). That's algebra!

im sorry but im so lost.... where does the -11246 come in? do i set it equal to the equation?

Since you now have \(r^n\), \(a\), and \(r\), you can use that formula that you used for #1 and #2.

Ohhhhh okay! I get it now!

SWEET! :) So, we'll both calculate #3 and see what we get....

I got -11 1/5

I got \(2255\)...
Let me use Wolfram Alpha to double check. Then I can show you a link to the math.

okay

http://www.wolframalpha.com/input/?i=11*%281-%28-11264%2F11%29%29%2F%281-%28-4%29%29

Maybe you just had some calculator error.

Oh I see what I did wrong

How would I go about starting the last one?

so would it be 10 (1-(781250/10))/1-r?

Sorry! Hi!

Its alright I disappeared for dinner so... haha

Which you can rearrange to spell \(r\ a\ n\): fun fact..

so it would be 8 *(1-78125)/(1-5) just to be sure
nice fun fact btw haha

Haha, thanks! And check your "\(r^n\)", or \(5^8\).

so 390625?

You got \(78125\) from \(r^{n-1}\), so I see where that came from :)
And, yep! \(390625\).

so that goes where i put the 78125

Yep!

It is \(r^n\), after all.

and your formula is\[\text{sum}=a\frac{(1-r^n)}{(1-r)}\]

I got 781,248 for my answer

I got the same! :) Congrats!

Any questions about this problem?

Nope I'm good! Thank you for your help!

You're welcome! Take care!