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

Need help on an arithmetic progression problem! Watch

    • Thread Starter
    Offline

    15
    ReputationRep:
    Name:  WP_20170114_19_52_48_Pro.jpg
Views: 13
Size:  273.6 KB

    I'm kinda stuck on this question, I'm not really sure on how to approach it, I've gotten pretty much nowhere so far.
    • Community Assistant
    Offline

    15
    ReputationRep:
    Sum from 1 to 2n minus the sum from 1 to n+2.
    What's the sum of the the first n integers?
    Offline

    20
    ReputationRep:
    the first term a is n+3

    there are 2n - ( n + 3 ) + 1 terms let us call this w

    do you know what is the difference d ?

    then use the formula Sw = w/2{2a + (w - 1) d}
    • Thread Starter
    Offline

    15
    ReputationRep:
    (Original post by the bear)
    the first term a is n+3

    there are 2n - ( n + 3 ) + 1 terms let us call this w

    do you know what is the difference d ?

    then use the formula Sw = w/2{2a + (w - 1) d}
    How did you find the number of terms, where did the plus one come from?
    Offline

    20
    ReputationRep:
    (Original post by Samii123)
    How did you find the number of terms, where did the plus one come from?
    if the terms were numbered 4,5,6,7,8 then there are not ( 8 - 4 ) terms but ( 8 - 4 ) + 1
    • Thread Starter
    Offline

    15
    ReputationRep:
    (Original post by the bear)
    if the terms were numbered 4,5,6,7,8 then there are not ( 8 - 4 ) terms but ( 8 - 4 ) + 1
    Ok, I've finally got it! Thank you so much for your help! It's just that I got confused with the last term of the series and the number of terms in the series.

    Edit: Arrrrrgh PRSOM
    Offline

    20
    ReputationRep:
    (Original post by Samii123)
    Ok, I've finally got it! Thank you so much for your help! It's just that I got confused with the last term of the series and the number of terms in the series.

    Edit: Arrrrrgh PRSOM
    don't worry we have all been there.
 
 
 
  • 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
    Did TEF Bronze Award affect your UCAS choices?
    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.