Hey there! Sign in to join this conversationNew here? Join for free
Turn on thread page Beta
    • Thread Starter
    Offline

    10
    ReputationRep:
    How would I go about a question if it's 'n' in the series and not 'r'? I'm doing question 10 (ii) but I don't understand the mark scheme.

    http://pmt.physicsandmathstutor.com/...%20Edexcel.pdf
    • Community Assistant
    Offline

    13
    ReputationRep:
    Community Assistant
    (Original post by amelienine)
    How would I go about a question if it's 'n' in the series and not 'r'? I'm doing question 10 (ii) but I don't understand the mark scheme.

    http://pmt.physicsandmathstutor.com/...%20Edexcel.pdf
    \sum\limits_{r=0}^n 2n means for each value of r, the corresponding term is 2n, which is independent of r. There are n+1 values of r.

    Hence \sum\limits_{r=0}^n 2n = 2n(n+1).
    • Thread Starter
    Offline

    10
    ReputationRep:
    (Original post by SherlockHolmes)
    \sum\limits_{r=0}^n 2n means for each value of r, the corresponding term is 2n, which is independent of r. There are n+1 values of r.

    Hence \sum\limits_{r=0}^n 2n = 2n(n+1).
    Why are there n+1 vales of r?
    • Community Assistant
    Offline

    13
    ReputationRep:
    Community Assistant
    (Original post by amelienine)
    Why are there n+1 vales of r?
    r = 0,1,...,n.

    I think of this as n values from 1 to n and then you add 1 for 0.
    • Thread Starter
    Offline

    10
    ReputationRep:
    (Original post by SherlockHolmes)
    r = 0,1,...,n.

    I think of this as n values from 1 to n and then you add 1 for 0.
    Oh okay, thank you!
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: January 15, 2017
Poll
“Yanny” or “Laurel”
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.