Turn on thread page Beta
    • Thread Starter
    Offline

    13
    ReputationRep:
    I have the sequence Ur = 1/2 r (r + 1)

    Somehow the sequence is 1, 3, 6, 10, 15.

    I understand how to get the recursive definition of Ur + 1 = Ur + r + 1 but don't have a clue with the first bit.

    Any help would be appreciated.
    Offline

    0
    ReputationRep:
    All its saying is The number you start with in the sequence is 1. So a is 1
    Ur is one
    So 1/2(1)(1+1) and you end up with =3
    then next number is 2, so 2 is r, with U2 looking like 1/2(2)(2+1) which gives you 3

    stick some more values in for 'r' and see what you get

    I think you may not like r as its used in geometric sequences as the common ratio?
    Offline

    0
    ReputationRep:
    When r = 1, 1/2 times 1 times 2 is 1
    When r = 2, 1/2 times 2 times 3 is 3
    When r = 3, 1/2 times 3 times 4 is 6

    etc
    • Thread Starter
    Offline

    13
    ReputationRep:
    (Original post by dexter -1)
    All its saying is The number you start with in the sequence is 1. So a is 1
    Ur is one
    So 1/2(1)(1+1) and you end up with =3
    then next number is 2, so 2 is r, with U2 looking like 1/2(2)(2+1) which gives you 3

    stick some more values in for 'r' and see what you get

    I think you may not like r as its used in geometric sequences as the common ratio?
    thanks
    • Thread Starter
    Offline

    13
    ReputationRep:
    (Original post by stevencarrwork)
    When r = 1, 1/2 times 1 times 2 is 1
    When r = 2, 1/2 times 2 times 3 is 3
    When r = 3, 1/2 times 3 times 4 is 6

    etc
    thanks
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: February 3, 2010

University open days

  1. University of Bradford
    University-wide Postgraduate
    Wed, 25 Jul '18
  2. University of Buckingham
    Psychology Taster Tutorial Undergraduate
    Wed, 25 Jul '18
  3. Bournemouth University
    Clearing Campus Visit Undergraduate
    Wed, 1 Aug '18
Poll
How are you feeling in the run-up to Results Day 2018?
Useful resources

Make your revision easier

Maths

Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

Equations

How to use LaTex

Writing equations the easy way

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