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

    13
    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

    13
    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

    13
    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

    13
    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.
 
 
 
  • 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
    Has a teacher ever helped you cheat?
    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

    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.