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Integration by substitution question

Question: Find the integral of 181x(1+x3) dx\displaystyle\int^8_1 \dfrac{1}{x(1+ \sqrt[3]{x})}\ dx using the substitution x = u3. I'm stuck at a step.

Here's how I tried to do it:
dx = 3u2 x du

121u3(1+u33) 3u2×du\Rightarrow \displaystyle\int^2_1 \dfrac{1}{u^3(1+ \sqrt[3]{u^3})}\ 3u^2 \times du
3121u(1+u) du\Rightarrow 3\displaystyle\int^2_1 \dfrac{1}{u(1+ u)}\ du

I don't know how to do it after that! Any help would be appreciated.
Split it into partial fractions :

A/u + B/(1+u) = 1/u(1+u)

Can you do it now ?
Reply 2
Original post by Ari Ben Canaan
Split it into partial fractions :

A/u + B/(1+u) = 1/u(1+u)

Can you do it now ?


Oops, I should've thought more on this question. Yes, I can do it now.
-Thanks
(edited 12 years ago)

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