Turn on thread page Beta
    • Thread Starter
    Offline

    17
    ReputationRep:
    this is from the latest ocr paper:

    given that: (x-p)(2x^2 +9x+10) = (x^2 - 4)(2x +q)

    for all values of x, find the constants of p and q.


    this is sooo hard for one of the first questions.
    can someone tell me how to work this out please
    Offline

    12
    ReputationRep:
    (Original post by cooldudeman)
    this is from the latest ocr paper:

    given that: (x-p)(2x^2 +9x+10) = (x^2 - 4)(2x +q)

    for all values of x, find the constants of p and q.


    this is sooo hard for one of the first questions.
    can someone tell me how to work this out please
    Hard???
    Just expand out and equate co-efficients.....
    • Thread Starter
    Offline

    17
    ReputationRep:
    (Original post by H.C. Chinaski)
    Hard???
    Just expand out and equate co-efficients.....
    sorry im still a newbie at C1. could you explain
    Offline

    0
    ReputationRep:
    (Original post by cooldudeman)
    sorry im still a newbie at C1. could you explain
    Expand the brackets for each side and then equate the terms which are the same, ie. all the x^2 terms, as they have to equal the same amount so for example for the x^2 terms, you get '9x^2-2px^2=qx^2', and when you have enough of these either there will be one with values that you can plug in or you solve using simultaneous equations.
    • Thread Starter
    Offline

    17
    ReputationRep:
    thanks
    Offline

    0
    ReputationRep:
    I remember this question, stared at it straight at the end with no clue on how to do it . I got it right though, I think one was 2 and the other was 5. I did what was mentioned above.
    Offline

    11
    ReputationRep:
    If you're having trouble with questions of a similar nature then I will suggest that you ask yourself if mathematics is really the subject for you...
    Offline

    14
    ReputationRep:
    (Original post by cooldudeman)
    this is from the latest ocr paper:

    given that: (x-p)(2x^2 +9x+10) = (x^2 - 4)(2x +q)

    for all values of x, find the constants of p and q.


    this is sooo hard for one of the first questions.
    can someone tell me how to work this out please
    I'd expand to get 2x^3 +9x^2 +10x -2px^2 -9px -10p = 2x^3 + qx^2 - 8x -4q

    Cancel 2x^3 to get 9x^2 +10x -2px^2 -9px -10p = qx^2 - 8x -4q
    then:

    10x - 9px = -8x so rearrange and stuff to get 9p = 18 (p=2)

    And 9x^2 - 2px^2 must equal qx^2

    So you get 9 - 2p = q and therefore 9-2(2) = q so q=5

    Then you can substitute these values in, rearrange the large equation and then solve the quadratic with a suitable method.


    Then
    • Thread Starter
    Offline

    17
    ReputationRep:
    (Original post by hassi94)
    I'd expand to get 2x^3 +9x^2 +10x -2px^2 -9px -10p = 2x^3 + qx^2 - 8x -4q

    Cancel 2x^3 to get 9x^2 +10x -2px^2 -9px -10p = qx^2 - 8x -4q
    then:

    10x - 9px = -8x so rearrange and stuff to get 9p = 18 (p=2)

    And 9x^2 - 2px^2 must equal qx^2

    So you get 9 - 2p = q and therefore 9-2(2) = q so q=5

    Then you can substitute these values in, rearrange the large equation and then solve the quadratic with a suitable method.


    Then
    yeah i understand, thanks for the help
    Offline

    0
    ReputationRep:
    give the chapter another read, think.
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: April 8, 2011

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.