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# c3 integration by substitution question watch

1. 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

2. so

can you go on from here?

if you substituging
then you need to integrate:
now substitute for all the e^x and you'll have something in which you only have u's
3. would (e^x)-2 be replaced with u-4
4. (Original post by akbarc)
would (e^x)-2 be replaced with u-4
Yes
5. i've got the answer as (u-4ln(u))/e^x . but this isn't the answer at the back of the book.
6. (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?
7. it's 2ln(2+e^x)-x +c

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