anonymous
  • anonymous
Given a geometric sequence whose sum of the first 10 terms is 4 and whose sum from the 11th to the 30th term is 48, find the sum from the 31st to the 60th term.
Geometry
katieb
  • katieb
See more answers at brainly.com
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 this expert

answer on brainly

SEE EXPERT ANSWER

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

cwrw238
  • cwrw238
Sum of 10 = a * (r^4 - 1) -------- = 4 r- 1
anonymous
  • anonymous
@cwrw238 why is it r^4? I thought it's r^10.
anonymous
  • anonymous
n is 10 not 4

Looking for something else?

Not the answer you are looking for? Search for more explanations.

More answers

amistre64
  • amistre64
hmm, given is: \[S_n=\frac{1-r^n}{1-r}\] \[S_{10}=4=\frac{1-r^{10}}{1-r}\] \[S_{30-10}=48=\frac{1-r^{20}}{1-r}\]
anonymous
  • anonymous
@hitten101 yes yes :)
shubhamsrg
  • shubhamsrg
you have been given the sum upto first 10 terms =4 you have also been given the sum upto first 30 terms = 4 + 48 =52 and you have 2 eqns with 2 variables ->solve for a and r now calculate sum for first 60 terms from that subtract sum of first 30 terms.. this should help..
anonymous
  • anonymous
|dw:1351514867224:dw|
anonymous
  • anonymous
a(r^10 - 1) / r - 1 = 4 a(r^30 - 1) / r - 1 = 52 ? @shubhamsrg like this?
anonymous
  • anonymous
solve for a and r.. then find the sum of 60 terms subtract sum of 30 terms from sum of 60 terms
shubhamsrg
  • shubhamsrg
@kmeds16 yep @hitten101 mistake in your formulla in the denominator..
anonymous
  • anonymous
I got, r^10 = 3. this is confusing :/ 10th root of 3?!
cwrw238
  • cwrw238
my mistake r^10 not r^4
shubhamsrg
  • shubhamsrg
how'd you get that? o.O
shubhamsrg
  • shubhamsrg
ahh k..got it
anonymous
  • anonymous
@kmeds16 @shubhamsrg yes no exponent in the denominator.. you are right
anonymous
  • anonymous
second equation divided by first equation. hehehehehe
shubhamsrg
  • shubhamsrg
your main aim is not to find r,, your main aim is to find sum.. leave it as r^10 = 3
anonymous
  • anonymous
find the sum of S60 and subtract 52, right?
shubhamsrg
  • shubhamsrg
seems likely..
shubhamsrg
  • shubhamsrg
do this,,this might simplify.. substitue r^10 =3 whereever you can leave r-1 as it is.. you can see a/(r-1) = 4/(r^10 -1) in calculation for sum of 60 terms ,make use of this eqn,, no need to find a.. :)
shubhamsrg
  • shubhamsrg
r^60 we all can find.. hmm.. hope that helped..
anonymous
  • anonymous
solving...hehehe ahm, thanks for the idea..

Looking for something else?

Not the answer you are looking for? Search for more explanations.