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Homework Help: Graphing functions and identifying features

  1. Aug 28, 2012 #1
    1. The problem statement, all variables and given/known data

    Hi there

    I need assistance with two graphs that are causing me some problems

    y=e(^-2x)(-1) and y=ln(x-2)+1

    2. Relevant equations

    I just need some guidence as to where to start - starting with a table - what range is approriate?

    3. The attempt at a solution

  2. jcsd
  3. Aug 28, 2012 #2


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    [itex]e^x[/itex] goes to 0 very rapidly for x< 0 and goes up very rapidly for x> 0. I would recommend taking x from -1 or -2 to +4 or +5.

    ln(x) is only defined for x> 0 so ln(x- 2) is only defined for x> 2. I would recommend taking x from 2 up to, say 10.

    Wouldn't it have been faster to just play around with some numbers rather than wait for someone to respond here? Do you not have a graphing calculator? It would have taken only a few seconds to try various value on a calculator.
  4. Aug 28, 2012 #3


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    Staff Emeritus
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    I assume you mean [itex]\displaystyle y=(-1)e^{-2x}\,,[/itex] which you could write as y = (e^(-2x))(-1), (the location of parentheses is important) or y = -e^(-2x), or better yet, y = -e-2x,

    and y = ln(x-2) + 1 .

    Are you familiar with the graphs of:
    [itex]\displaystyle y=e^{x}\,,[/itex]​
    [itex]\displaystyle y=\ln(x)\ ?[/itex]​
    That's the place to start.

    Then use what you've (hopefully) been learning about shifting, stretching, shrinking, flipping, etc. graphs.
  5. Aug 28, 2012 #4
    Thank you, yes, you are right. I think just a lack of confidence in this aspect of Maths. Sorry to be a bother. Regards
  6. Aug 28, 2012 #5
    Many thanks, I appreciate the guidance.
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