what does the geometric sequance formula look like? and can the geometric (series) formula find the sum of a geo sequance problem??

Question

anonymous · Answer

http://tutorial.math.lamar.edu/Classes/CalcII/Series_Special.aspx

anonymous · Answer

where is the formula?

amistre64 · Answer

there are 2 versions of it that i can recall

$$A_{n+1}=A_n*r$$$$A_n=A_1*r^{n-1}$$

anonymous · Answer

oh, okay. can these formulas solve lets say for example: What is the sum of the geometric sequence 8, –16, 32 … if there are 15 terms?

amistre64 · Answer

not as is; they just allow us to find the terms of the sequence itself

a series (adding up the terms of the seq) goes by another formula
$$a\frac{1-r^n}{1-r}$$

amistre64 · Answer

a, in this case, is the first term

anonymous · Answer

so that would be the formula I would use for that problem?

amistre64 · Answer

if you want to add up all the terms; then yes

amistre64 · Answer

a = 8, r=-16/8, and n=15

right?

anonymous · Answer

yep, and then I just pulg them in for the terms.

amistre64 · Answer

correct

anonymous · Answer

would this be my answer? 87,384?

amistre64 · Answer

http://www.google.com/search?sugexp=chrome,mod=18&sourceid=chrome&ie=UTF-8&q=19*sqrt(4*154*22%2F7)#hl=en&gs_nf=1&gs_mss=8(1-(-2)%5E15)%2F&pq=19*sqrt(4*154*22%2F7)&cp=17&gs_id=2t&xhr=t&q=8(1-(-2)%5E15)/(1%2B2)&pf=p&sclient=psy-ab&oq=8(1-(-2)%5E15)/(1%2B2)&gs_l=&pbx=1&bav=on.2,or.r_gc.r_pw.r_qf.,cf.osb&fp=dddf8a6dafb67f55&biw=1280&bih=675 google calculator says ..... yes!! :)

anonymous · Answer

lol thank you, at least yu took the time to help me :)

amistre64 · Answer

youre welcome, and good luck :)