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Math Help - Drug Absorption

  1. #1
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    Drug Absorption

    A drug is administered intravenously for pain. The function
    f(t)=90 - 52 ln (1 + t), 0<t<4 gives the number of units of the drug in the body after t hours.

    a. What was the initial number of units of the drug administered?
    b. How much is present after 2 hours.
    c. Draw the graph of f.


    In part a, you substitute t for 0. So you have 90-52 ln (1 + 0). and i know that Ln1 aways = 0 . So 90-52n(1) = 90. i don't know just doesn't sound right to me for some reason. Then you plug in 2 for t. I have a feeing there's some set method for answering this kind of equation but it evades me.
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  2. #2
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    Quote Originally Posted by fezz349 View Post
    A drug is administered intravenously for pain. The function
    f(t)=90 - 52 ln (1 + t), 0<t<4 gives the number of units of the drug in the body after t hours.

    a. What was the initial number of units of the drug administered?
    b. How much is present after 2 hours.
    c. Draw the graph of f.


    In part a, you substitute t for 0. So you have 90-52 ln (1 + 0). and i know that Ln1 aways = 0 . So 90-52n(1) = 90. i don't know just doesn't sound right to me for some reason. Then you plug in 2 for t. I have a feeing there's some set method for answering this kind of equation but it evades me.
    Your method is correct. Why would you doubt it?
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  3. #3
    Senior Member pacman's Avatar
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    fezz349, you are almost there;

    f(t)=90 - 52 ln (1 + t), 0<t<4

    a) for t = 0 hour,

    f(0) = 90 - 52 ln(1 +0) = 90 - 0 = 90 units of drug present

    b) for t = 2 hours;

    f(2) = 90 - 52 ln(1 + 2)

    = 90 - 52 ln 3

    = 90 - 52(1.0986)

    = 90 - 57.13

    = 32.87 units of drug remaining

    c) See below,



    Attached Thumbnails Attached Thumbnails Drug Absorption-log.gif  
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  4. #4
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    alright thanks guys, it just seemed a little too straightforward, i guess every question isn't trying to trick u
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