# Can somebody help me on integration?

• February 11th 2013, 10:46 AM
Levani
Can somebody help me on integration?
how do i integrate this? : t / (t+88) ?? i could rewrite it like this : 1 - (88/t+88) but i dont know how to integrate that. i dont think i can substitude anything.
• February 11th 2013, 11:06 AM
MathJack
Re: Can somebody help me on integration?
let u = t + 88, then, du = dt,

so expression is now (u-88)/u .du, or (1 - 88/u)du

now this is simple to integrate.
dont forget to sub back in after integration
• February 11th 2013, 11:07 AM
ebaines
Re: Can somebody help me on integration?
Substitute u = t+88:

t = u-88
du = dt

$\int \frac {t}{t+88} dt = \int \frac {u-88}{u} du = \int (1 - \frac {88} u) du$

$= u - 88 \ln (u) = t+88-88 \ln (t+88)$
• February 11th 2013, 11:21 AM
Levani
Re: Can somebody help me on integration?
thank u but i dont get how did u go from INT( 1 - 88/u ) du to u - 88*ln(u) ?
which formula did u use, i cant find it on integral table
• February 11th 2013, 11:25 AM
MathJack
Re: Can somebody help me on integration?
factor out 88 so u have 88(int) 1/u which is in is the natural log of u. In tables too. Please thank me
• February 11th 2013, 11:40 AM
Levani
Re: Can somebody help me on integration?
oh i got it :D u take 88 out of integral