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    needed some help on a c3 integration by substitution question. integrate using substitution: ((e^x)-2)/((e^x)+2). i'm using e^x plus 2 as the substitution because it's raised to the power of -1 but i can't seem to get the correct answer. thanks
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    u = e^x +2
    so u-2 = e^x

    can you go on from here?

    if you substituging u= x^x+2
    then you need to integrate: \frac{e^x - 2}{u} \times \frac{du}{e^x}
    now substitute u-2 = e^x for all the e^x and you'll have something in which you only have u's
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    would (e^x)-2 be replaced with u-4
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    (Original post by akbarc)
    would (e^x)-2 be replaced with u-4
    Yes
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    i've got the answer as (u-4ln(u))/e^x . but this isn't the answer at the back of the book.
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    (Original post by akbarc)
    i've got the answer as (u-4ln(u))/e^x . but this isn't the answer at the back of the book.
    what is the answer in the back of the book?
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    it's 2ln(2+e^x)-x +c
 
 
 
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