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

C3 Functions Watch

Announcements
    • Thread Starter
    Offline

    11
    ReputationRep:
    http://www.madasmaths.com/archive/iy...apers/c3_f.pdf

    Need help in part 8(c), how do we get the range over here as 0<f(x)<4? I tend to get confused when finding the range and domain of such situations. Could anyone tell me how to do so? TIA.
    Offline

    3
    (Original post by sabahshahed294)
    http://www.madasmaths.com/archive/iy...apers/c3_f.pdf

    Need help in part 8(c), how do we get the range over here as 0<f(x)<4? I tend to get confused when finding the range and domain of such situations. Could anyone tell me how to do so? TIA.
    Draw a graph?
    For x > 1, the denominator is increasing as x increases, so f(x) is decreasing.
    As x tends to infinity, f(x) gets smaller and closer to zero.
    Then evaluate f(1).
    • Thread Starter
    Offline

    11
    ReputationRep:
    (Original post by EricPiphany)
    Draw a graph?
    For x > 1, the denominator is increasing as x increases, so f(x) is decreasing.
    As x tends to infinity, f(x) gets smaller and closer to zero.
    Then evaluate f(1).
    So, you simply substituted x=1? Or you came to a conclusion by drawing out a graph?
    • Community Assistant
    • Welcome Squad
    Offline

    19
    ReputationRep:
    (Original post by sabahshahed294)
    So, you simply substituted x=1? Or you came to a conclusion by drawing out a graph?
    Yes, substitution. Look at the graph, you don't even need to draw it. x>1 shows that you can ignore the left branch of it and since it is beyond the asymptote, the range will not involve infinity. So you can plug in x=1 and it will be everything between (and excluding including) f(1) and 0.
    • Thread Starter
    Offline

    11
    ReputationRep:
    (Original post by RDKGames)
    Yes, substitution. Look at the graph, you don't even need to draw it. x>1 shows that you can ignore the left branch of it and since it is beyond the asymptote, the range will not involve infinity. So you can plug in x=1 and it will be everything between (and excluding including) f(1) and 0.
    Alright! Thank you.
 
 
 
  • 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
    Break up or unrequited love?
    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.