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

    3
    ReputationRep:
    Describe a sequence of two geometrical transformations that maps the graph of y=f(x) onto the graph of y=f(2x+2).

    The answer is a stretch of scale factor 1/2 in the x direction followed by a translation one unit to the left. I get this because it's like you go f(x) -> f(2x) -> f2(x+1) so f(2x+2).

    My answer was wrong because I put them the other way round. I thought that I could say a translation one unit to the left giving f(x+1) followed by a stretch sf 1/2 in x direction giving f2(x+1) and therefore the answer.

    Am I right in saying that such a combination actually gives you f(2x+1)? Because the stretch means replacing x with 2x rather than multiplying the whole thing by 2? I hope that made sense to somebody lol
    Offline

    1
    ReputationRep:
    The 2 only affects the x, not the 1.
    • Thread Starter
    Offline

    3
    ReputationRep:
    (Original post by hannah412)
    The 2 only affects the x, not the 1.
    Cool I thought that might be it. Thanks
    Offline

    20
    ReputationRep:
    i would say translate 2 left then squash 1/2 horizontally ?

    :beard:
    • Thread Starter
    Offline

    3
    ReputationRep:
    (Original post by the bear)
    i would say translate 2 left then squash 1/2 horizontally ?

    :beard:
    Yeah that works too! My confusion was with thinking the stretch affected more than just the x.
    Offline

    15
    ReputationRep:
    (Original post by the bear)
    i would say translate 2 left then squash 1/2 horizontally ?

    :beard:
    I tend to aswell. Means you don't have the stretch to worry about.
    Offline

    2
    ReputationRep:
    Never say "squash". Mark schemes are clear that it must be "stretch".
    Offline

    19
    ReputationRep:
    it can be written correctly 2 different ways, but only one way is sensible (the other is for maths perverts)
    Offline

    2
    ReputationRep:
    Page 10 of ocr.org.uk/Images/60809-examiners-reports-january.pdf says candidates must say "one-way stretch", not "squash" or "squeeze".
    Offline

    13
    ReputationRep:
    (Original post by TeeEm)
    it can be written correctly 2 different ways, but only one way is sensible (the other is for maths perverts)
    Is it true to say that you can look at what's happening in the brackets first and mention the translation before the stretch and then you look outside the brackets and do the stretch before the translation.

    e.g. x^2 to 2(3x-6)^2 -4 would be
    translation in x by 6
    stretch in x sf 1/3
    stretch in y sf 2
    translate in y by -4
    Offline

    2
    ReputationRep:
    yes I think so.
 
 
 
Poll
Do you agree with the PM's proposal to cut tuition fees for some courses?
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.