Hey there! Sign in to join this conversationNew here? Join for free

C2 Geometric Series Watch

Announcements
    • Thread Starter
    Offline

    8
    ReputationRep:
    I found a question in this paper (I'll add the link) which I'm not really sure how to answer. It is on geometric series and is Q7. Parts a) and b) are fine but I can't get my head around how to do part c). If a is 1/2 surely r is 3/2 and there can be no clear sum to infinity? The formula only works when the mod of r is less than 1, right? Help....

    https://crashmaths.com/wp-content/up.../C2PPAQPV2.pdf
    Offline

    18
    ReputationRep:
    Apachai Hopachai can you help? i clearly cant
    Offline

    20
    ReputationRep:
    (Original post by Bulbasaur10)
    I found a question in this paper (I'll add the link) which I'm not really sure how to answer. It is on geometric series and is Q7. Parts a) and b) are fine but I can't get my head around how to do part c). If a is 1/2 surely r is 3/2 and there can be no clear sum to infinity? The formula only works when the mod of r is less than 1, right? Help....

    https://crashmaths.com/wp-content/up.../C2PPAQPV2.pdf
    the sum to infinity is -1 if you put a/( 1 - ( a + 1 ))

    so you want to make Sn < -1
    • Thread Starter
    Offline

    8
    ReputationRep:
    (Original post by the bear)
    the sum to infinity is -1 if you put a/( 1 - ( a + 1 ))

    so you want to make Sn < -1
    Yeah that's what I thought but the mark scheme says 1, and -1 would not make sense considering every term in the series is positive.
    Offline

    20
    ReputationRep:
    (Original post by Bulbasaur10)
    Yeah that's what I thought but the mark scheme says 1, and -1 would not make sense considering every term in the series is positive.
    there are quite a few errors in the crashmaths papers :dontknow:
    • Thread Starter
    Offline

    8
    ReputationRep:
    (Original post by the bear)
    there are quite a few errors in the crashmaths papers :dontknow:
    Ach... yeah. Thanks for warning me They seem to be pretty useful to an extent though. It probably is just an error.
    Offline

    20
    ReputationRep:
    (Original post by Bulbasaur10)
    Ach... yeah. Thanks for warning me They seem to be pretty useful to an extent though. It probably is just an error.
    the gcse papers for the new 9-1 fiasco bold new approach to exams are great.
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    Will you be richer or poorer than your parents?
    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
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • 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

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