A community for students.
Here's the question you clicked on:
 0 viewing
anonymous
 5 years ago
What is the nth term of the sequence 3, 11, 31, 69, 131?
anonymous
 5 years ago
What is the nth term of the sequence 3, 11, 31, 69, 131?

This Question is Closed

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0Have you tried some sort of finite difference method?

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0I had a look at it, and I'm thinking the nth term is a polynomial in n.

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0If you set it up as: 3 11 31 69 131 8 20 38 62 12 18 24 6 6 0

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0If you take the first line as some function of n, f(n) (i.e. zeroth derivative), then the fifth line will be the fourth derivative and you can start integrating back up. So\[\frac{d^4f(n)}{dn^4}=0 \rightarrow \frac{d^3f(n)}{dn^3}=c_1 \rightarrow \frac{d^2f(n)}{dn^2}=c_1n+c_2\]\[\rightarrow \frac{df(n)}{dn}=\frac{c_1n^2}{2}+c_2n+c_3 \]\[\rightarrow f(n)=\frac{c_1}{6}n^3+\frac{c_2}{2}n^2+c_3n+c_4\]

anonymous
 5 years ago
Best ResponseYou've already chosen the best response.0You can then set up four linear equations with the first four terms and solve for the coefficients. I did this with a matrix calculator. When I tested for the 5th term, it spat out 130.29. The discrepancy probably due to error in rounding at each step.
Ask your own question
Sign UpFind more explanations on OpenStudy
Your question is ready. Sign up for free to start getting answers.
spraguer
(Moderator)
5
→ View Detailed Profile
is replying to Can someone tell me what button the professor is hitting...
23
 Teamwork 19 Teammate
 Problem Solving 19 Hero
 Engagement 19 Mad Hatter
 You have blocked this person.
 ✔ You're a fan Checking fan status...
Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.