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Please help I need to make sure on this

  1. Jan 3, 2005 #1


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    Hi i am new here, and just wondering if my answers are right, please check for me.

    1. Evaluate g(x) = x^2 + x
    g(x + 3)
    my answer: x^2 + 7x -12

    2. Function or not:
    x^2 = y - 3
    I say not a function.

    3. y^2 = x - y
    I would say yes this is a function.

    thanks a lot
    Last edited: Jan 3, 2005
  2. jcsd
  3. Jan 3, 2005 #2


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    1. why minus 12 and not plus 12?

    2. x(y) is not a function but y(x) is a function.

    3. x(y) is a function. Although you cannot re-write this expression as a function y of x, you can see from the graph of x(y) that to each x correspond two different y. This means, by the definition of a function that y(x) is not a function.

    reply if you want further explanations.
  4. Jan 3, 2005 #3


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    2. WHY would you say it is not a function?

    3. WHY would you say it is a function?

    Crucial to answering both those questions: what is the DEFINITION of "function"?
  5. Jan 3, 2005 #4


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    for the first one I figured it out to plus 12 also, but when I check the solution it is -12, so i guess the book is wrong. I understand about function now thanks
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