Question

Which method of integration do you need to use to integrate: 9ln(x)/x^2 ?

Answer 1

substitute

Answer 2

sometimes it's just staring you right in the eye ^.^

Answer 3

subsitute what? if we let u = ln (x), du = 1/x

Answer 4

yeah? And what's wrong with that? :D

Answer 5

your integral will be in terms of u and x not u only. You can't integrate it.

Answer 6

oh jeez :D
If we let u = ln(x)
\[\Large \int \frac{9\ln(x)}{x^2}dx \rightarrow \int \frac{9u}{x}du\rightarrow \int \frac{9u}{e^u}du\]
Happy? :D

Answer 7

\[\LARGE \rightarrow \int 9ue^{-u}du\]
Let's do this by parts... when we feel like it ^.^

ta

Answer 8

Okay thanks!

Answer 9

Hold on A SEC

Answer 10

\[9\int\limits_{}^{}lnx*\frac{ 1 }{ x^2 }=-9\int\limits_{}^{}lnx*(\frac{ 1 }{ x })'=-9[lnx*\frac{ 1 }{ x}-\int\limits_{}^{}\frac{ 1 }{ x^2 }]\]
\[=-9[\frac{ lnx+1 }{ x}]+\zeta\]

Answer 11

I've used the integration by parts