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

    0
    ReputationRep:
    C3 retake tomorrow....
    Offline

    3
    ReputationRep:
    I'm scared to death. :puke:
    Offline

    18
    ReputationRep:
    I want an A*. I'm not gonna get one.
    Offline

    2
    ReputationRep:
    The last question in arseys answers is wrong when asked to find the range of fg(x) it is greater or equal to 3
    Offline

    7
    (Original post by RamsFanNo1)
    The last question in arseys answers is wrong when asked to find the range of fg(x) it is greater or equal to 3
    oh for heavens sake not this again

    it is NOT >= 3 it is just >3

    I had to explain why several times, if you don't believe me look in the official mark scheme.

    If you don't understand why, you don't understand functions fully.
    Offline

    3
    ReputationRep:
    (Original post by Arsey)
    oh for heavens sake not this again

    it is NOT >= 3 it is just >3

    I had to explain why several times, if you don't believe me look in the official mark scheme.

    If you don't understand why, you don't understand functions fully.
    I fully understand functions, but anyways.. I've got a question. When the question asks me to find fg(x) or gf(x) and then it asks me its to find range/ domain what do i need to consider?

    Help would be highly appreciated.
    Offline

    7
    I think the easiest thing to do is to draw a flow chart and sketch the graphs

    fg(x) works like this

    input value x ----> function g ------> g(x) -------> function f ------> fg(x)


    so your input value x has to belong to the domain of g

    the range of g(x) (possible solutions / possible y coordinates) goes into function f but these solutions also have to belong to the domain of f. So only numbers which are BOTH in the range of g(x) and domain of f(x) will go into the second function f.

    The possible answers are the range of fg(x)


    Try substituting values into g and the solutions of that into f to see what is acceptable if you are unsure.

    The key thing to remember that it isn't always as simple as to sketch the graph of the composite function and then look at the graph for the range of the composite function.

    restrictions on the domains of the original function could have an impact.
    Offline

    2
    ReputationRep:
    (Original post by Arsey)
    oh for heavens sake not this again

    it is NOT >= 3 it is just >3

    I had to explain why several times, if you don't believe me look in the official mark scheme.

    If you don't understand why, you don't understand functions fully.
    Sorry I just properly read the question and saw that the domain of g(x) > 1 - again I am very sorry!!
    Offline

    12
    ReputationRep:
    Oh god. This is going to be a tough cookie. I need to get an A*!
 
 
 
Poll
Do you agree with the PM's proposal to cut tuition fees for some courses?

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.