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Quote:

Originally Posted by taichi2910

Hello Guys dont know if this is the right forum for this questio, but i do really need your help on them

integrate:

a) by substitution :

integral(4 x/sqrt(8 x^2-1), x, 1, 2)

let $u=8x^2-1 \implies du=16xdx \iff \frac{du}{16}=dx$

$<br /> \int_{1}^{2}\frac{4x}{8x^2-1}dx=\frac{1}{4}\int_{7}^{31}\frac{1}{u}du<br />$

You should be able to finish from here.