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PR 1024 Functions #6

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CR Just gettin' started!
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PR 1024 Functions #6 Post Wed Apr 11, 2012 9:47 am
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    Hi all,

    Wondering if someone can help me understand this, its the first Q in this book to stump me..
    Page 164
    http://books.google.ca/books?id=-9wUwATGS2kC&printsec=frontcover#v=onepage&q&f=true is the digital free look at the Q

    f(x) = x^2 + x
    f(y) = ?
    (1) $y = 3(($10)+30)
    (2) $y = $($(4))

    Answer is apparently D both sufficient though when looking at the solution it makes absolutely no sense to me... (soln on page 211)

    I am convinced this is a book error unless someone can explain why it isnt.

    Thanks!!

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    Post Thu Apr 12, 2012 1:04 am
    CR wrote:
    Hi all,

    Wondering if someone can help me understand this, its the first Q in this book to stump me..
    Page 164
    http://books.google.ca/books?id=-9wUwATGS2kC&printsec=frontcover#v=onepage&q&f=true is the digital free look at the Q

    f(x) = x^2 + x
    f(y) = ?
    (1) $y = 3(($10)+30)
    (2) $y = $($(4))

    Answer is apparently D both sufficient though when looking at the solution it makes absolutely no sense to me... (soln on page 211)

    I am convinced this is a book error unless someone can explain why it isnt.

    Thanks!!
    can you pl. put down the question?

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    CR Just gettin' started!
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    Post Thu Apr 12, 2012 6:20 am
    put down the question? You want me to remove the link?

    The question and link to the Q are in the post..

    Shalabh's Quants Really wants to Beat The GMAT!
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    Post Thu Apr 12, 2012 7:40 am
    CR wrote:
    put down the question? You want me to remove the link?

    The question and link to the Q are in the post..
    No.I mean can you pl. post the question? I cannot access the question via link. I will surely help dear! Very Happy

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    Shalabh Jain,
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    CR Just gettin' started!
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    Post Thu Apr 12, 2012 9:46 am
    The question is in the first post Smile

    Its a Data Sufficiency Q, it literally reads as:
    F at x = x squared plus x
    what is F at y?

    f(x) = x^2 + x
    f(y) = ?

    Scenario 1: weird dollar symbol y = 3 multiplied by ( ( weird dollar symbol 10) plus 30)
    Scenario 2: weird dollar symbol y = weird dollar symbol multiplied by ( ( weird dollar symbol multiplied by 4))
    (1) $y = 3(($10)+30)
    (2) $y = $($(4))

    The scenarios don't even follow the same function at x pattern... very odd.

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    Stuart Kovinsky GMAT Instructor
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    Post Thu Apr 12, 2012 11:01 am
    Hi!

    The question makes no sense as you've posted it. Unfortunately, p164 is omitted from that preview of the book, so there's no way to check the actual question.

    Here's how the question likely reads in order for (D) to be correct:

    If f(x) = x^2 + x for all values of x, what's f(y)?

    (1) f(y) = 3(f(10) + 30)
    (2) f(y) = f(f(4))

    We know that f(x) = x^2 + x for all values of x, accordingly, we know that:

    f(y) = y^2 + y

    To solve, therefore, we need a value for y or a way to solve for f(y) directly.

    (1) f(y) = some ugly equation we can turn into a number (using the function provided) - sufficient.
    (2) f(y) = a double application of the function with a number provided, so we can solve - sufficient.

    Accordingly, each statement is sufficient alone - choose (D).

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