Hey there! Sign in to join this conversationNew here? Join for free
    • Thread Starter
    Offline

    15
    ReputationRep:
    http://mathsathawthorn.pbworks.com/f/FP1Jun06.pdf
    Could someone teach me how to start on q4?
    The last time I did geometric series was in core 2 but ive forgot them:/
    Is it a,ar, ar^2?
    Offline

    16
    ReputationRep:
    Form of a geometric series:

    a + ar + ar^2

    We know that the common ratio, r, is 2, so:

    a + 2a + 4a.

    This means that the first root is equal a, the second, 2a, and the third, 4a.
    • Community Assistant
    • Welcome Squad
    Online

    20
    ReputationRep:
    Community Assistant
    Welcome Squad
    (Original post by English-help)
    http://mathsathawthorn.pbworks.com/f/FP1Jun06.pdf
    Could someone teach me how to start on q4?
    The last time I did geometric series was in core 2 but ive forgot them:/
    Is it a,ar, ar^2?
    Yes the roots would be a, 2a, 2^2a such that a>0 in order for them to be positive.

    Then just equate \displaystyle \sum \alpha \beta = 56 from your knowledge of roots of cubic polynomials, and solve for a.
    • Thread Starter
    Offline

    15
    ReputationRep:
    (Original post by RDKGames)
    Yes the roots would be a, 2a, 2^2a such that a>0 in order for them to be positive.

    Then just equate \displaystyle \sum \alpha \beta = 56 from your knowledge of roots of cubic polynomials, and solve for a.
    Okayy good
 
 
 
  • 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
    Would you like to hibernate through the winter months?
    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.