Turn on thread page Beta
    • Thread Starter

    Hello my fellow mathematicians

    I was wondering if you all could help me out with a problem O_O...well 2 really xD

    1.) let S(N) = sigma (with 'N' on top and 'n=1' on the bottom) (-1)^(n-1) * n^3

    Find S(2N) in terms of N, simplifying your answer as far as possible.

    Hence write down an expression for S(2N+1) and find the limit, as N -> (infinity), of [S(2N+1) / N^3]

    2.) It is given that I(n) = integral (boundaries of 1 and 0) (1+x^3)^(-n) dx where n>0

    Show that:
    d/dx[x(1+x^3)^(-n)] = -(3n-1)(1+x^3)^(-n) + 3n(1+x^3)^(-n-1) and hence or otherwise show that...

    I(n+1) = 2^(-n)/(3n) + (1+ (1/(3n))I(n)

    Thank you soo much guys ...I would like detailed working as to how you guys arrived at your answer because I really need to know :|
    • Thread Starter

    I've been looking all over the internet as to how to solve these questions but I'm not getting any luck...so can you guys please help

    That's not how it works around here, you must first show your working so we can try to nudge you in the right direction with subtle hints.
Submit reply
Turn on thread page Beta
Updated: September 29, 2011

University open days

  • University of Bradford
    All faculties Undergraduate
    Wed, 21 Nov '18
  • Buckinghamshire New University
    All Faculties Postgraduate
    Wed, 21 Nov '18
  • Heriot-Watt University
    All Schools Postgraduate
    Wed, 21 Nov '18
Black Friday: Yay or Nay?
Useful resources

Make your revision easier


Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here


How to use LaTex

Writing equations the easy way


Best calculators for A level Maths

Tips on which model to get

Student revising

Study habits of A* students

Top tips from students who have already aced their exams

Study Planner

Create your own Study Planner

Never miss a deadline again

Polling station sign

Thinking about a maths degree?

Chat with other maths applicants

Can you help? Study help unanswered threads

Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.