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Math Help - Algebra- what went wrong?

  1. #1
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    Algebra- what went wrong?

    Ok I had to find the derivitive of some ugly equation, and I started simplifying till I got to this point:


    If I substitute t for 2, then I get an answer of about 34, which is the answer I need, however, when I continued to simplify:


    But when I sub 2 for t now, my answer is 74? Where did I go wrong in my simplifying.
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  2. #2
    Super Member angel.white's Avatar
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    Quote Originally Posted by iphysics View Post
    Ok I had to find the derivitive of some ugly equation, and I started simplifying till I got to this point:


    If I substitute t for 2, then I get an answer of about 34, which is the answer I need, however, when I continued to simplify:


    But when I sub 2 for t now, my answer is 74? Where did I go wrong in my simplifying.
    For the numerator:
    -ln(t/4+1)*2t(t+4)~~~~~=~~~~~ -ln(t/4+1)*2t^2 -ln(t/4+1)*8t

    For the denominator:
    I'm not sure what you were shooting for, but \frac{t+4}{(t^2+25)^2} does not equal (t+4)(t^2+25)^2

    for example, a=t+4, b=(t^2+25)^2

    Then you have the denominator as a divided by b equals a times b. Since division and multiplication are not the same thing, this is not true.
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  3. #3
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    Nevermind I got it!!

    Thanks for your help anyway
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