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Math Help - Composite function question

  1. #1
    s3a
    s3a is offline
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    Composite function question

    My question is on #9. I GOT THE ANSWER which is:

    384t^2 + 73.6t - 8.64

    and

    5.935473877 hours

    but my question is WHY I use the composite function in order to answer that question.

    The question asks for time from a function N that measures number of bacteria. However, in N(T(t)) T(t) is temperature and not time.

    Can someone please explain this to me?

    Any help would be greatly appreciated!
    Thanks in advance!
    Attached Thumbnails Attached Thumbnails Composite function question-temp.jpg  
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  2. #2
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    you need to use the composite function because they ask you a question about time, and as you said N itself is a function of temperature, but since temp is a function of time, N is really a function of time but only if you use the composite function


    you could have found the temperature when N=13960, and then set that answer equal to 4t+1.3 to find the time, by using the composite you skip this extra step
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