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Math Help - Trouble with graphi and asymptotes

  1. #1
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    Trouble with graphi and asymptotes

    4. a) Find all horizontal and vertical asymptotes of f(x)= -x / (x+1)(x-3) and sketch it's graph.

    There should be two vertical asymptotes, x=-1 and x=3. I used multiple graph calculators online and they do not show the x=3 asymptote.

    What am I doing wrong?
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  2. #2
    Super Member bigwave's Avatar
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    Quote Originally Posted by thekrown View Post
    4. a) Find all horizontal and vertical asymptotes of f(x)= -x / (x+1)(x-3) and sketch it's graph.

    There should be two vertical asymptotes, x=-1 and x=3. I used multiple graph calculators online and they do not show the x=3 asymptote.

    What am I doing wrong?
    most calculators will not show the asymptotes because there is a hole in the function. there may appear to be an asymptote sometimes due the screen resolution and a jump from a long distance between points.
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  3. #3
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    Okay so am I correct with this answer:

    Horizontal Asymptote
    when x gets big+ y gets close to 0-
    when x gets big- y gets close to 0+

    Vertical Asymptote
    x gets close to 3+ y gets big -
    " " " " 3- y gets big +
    " " " " -1+ y gets big -
    " " " " -1- y gets big +
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  4. #4
    Super Member bigwave's Avatar
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    yes it appears so

    if you haven't ever used this you might like

    - Wolfram|Alpha

    where I graphed your equation

    this ussually gives more info about what's going on.
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  5. #5
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    Thanks for your help, it's good to know I'm not crazy after all.
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