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Thread: Which expression is defined for all real numbers?

  1. #1
    Newbie rjg247's Avatar
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    Which expression is defined for all real numbers?

    Which expression is defined for all real numbers?
    Please explain why the choice that you chose is correct.

    Choice 1)
    x+3/x^2

    Choice 2)
    4/(x-2)^2

    Choice 3)
    5/(x+2)^2

    Choice 4)
    7/x^2+3
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  2. #2
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    Re: Which expression is defined for all real numbers?

    So what are your thoughts?
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    Re: Which expression is defined for all real numbers?

    big hint: cannot divide by zero

    so, what do you think?
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    Newbie rjg247's Avatar
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    Re: Which expression is defined for all real numbers?

    Quote Originally Posted by skeeter View Post
    big hint: cannot divide by zero

    so, what do you think?
    In that case, would it be choice 1 since x could be 0? I still do not understand the question tho.
    Last edited by rjg247; Sep 7th 2015 at 11:56 AM.
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    Re: Which expression is defined for all real numbers?

    Quote Originally Posted by rjg247 View Post
    In that case, would it be choice 1 since x could be 0. I still do not understand the question tho.
    I said, ... cannot divide by zero. Division by zero is undefined.
    Last edited by skeeter; Sep 7th 2015 at 11:59 AM.
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    Forum Admin topsquark's Avatar
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    Re: Which expression is defined for all real numbers?

    They are asking which of the choices is not defined for all real numbers. skeeter told you that you can't divide by 0. So in choice 1 can we let x = 0?

    Also, please use parenthesis.

    Choice 1 reads x + \frac{3}{x^2} and I'm betting it's supposed to be \frac{x+3}{x^2}. These are very different expressions. What you need to write in this case is (x + 3)/x^2.

    Similarly choice 4 reads \frac{7}{x^2} + 3. Again I'm guessing it's supposed to be \frac{7}{x^2 + 3}. What you need to write in this case is 7/(x^2 + 3).

    -Dan
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