Turn on thread page Beta

Can you answer this composite functions question? watch

    • Thread Starter
    Offline

    6
    ReputationRep:
    Given that for all values of x,

    f(x) = 3x+p
    g(x) = px+4
    and fg(x) = 6x+q

    where p and q are constants.

    Work out the values of p and q.
    Offline

    5
    ReputationRep:
    p = 2 and q = 14

    Also where did you get this question from? And what exam board are you doing for Math?
    Offline

    22
    ReputationRep:
    (Original post by ky_1652)
    p = 2 and q = 14

    Also where did you get this question from? And what exam board are you doing for Math?
    provide working out you donkey.
    Offline

    6
    ReputationRep:
    (Original post by Sanket.z.meerkat)
    Given that for all values of x,

    f(x) = 3x+p
    g(x) = px+4
    and fg(x) = 6x+q

    where p and q are constants.

    Work out the values of p and q.
    Hi, so firstly as it is composite you need to put g in F. So 3(px+4) + p

    Expand and simplify to get

    3px + 12 + p
    Then make that equal to fg[x] you were given

    3px+12+p = 6x + q

    Compare coefficients of x

    3p=6 so p=2. Then 12+p = q so q = 14

    Hope that is clear
    Offline

    5
    ReputationRep:
    (Original post by BTAnonymous)
    provide working out you donkey.
    Offline

    13
    ReputationRep:
    you can write fg (x) as f [g (x)] so this will mean;
    fg (x) = 3 (g (x)) + p
    fg (x) = 3 (px + 4) + p
    fg (x) = 3px + 12 +p
    now the trick given is the coefficient of x in fg (x) they have given...the coefficient is 6 that means that p has to be a number that when multiplied by 3 we get 6 and that means p = 2 and u can get q by 12 + p....
    hope you understand this 😊
    Posted on the TSR App. Download from Apple or Google Play
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: February 19, 2018

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.