Question

Would I have to use the 'u' substitution method to solve this integral?

Answer 1

can you try without u-sub?

Answer 2

Ye, u = lnx

Answer 3

@nincompoop lol no clue

Answer 4

You can pull the -9 out as it's just a constant

Answer 5

Ohh right! I always forget that! >.<

Answer 6

\[-9 \int\limits \frac{ \left( lnx \right)^2 }{ x } dx\] u = lnx

Answer 7

then dx = (1/x) du

Answer 8

\[du = \frac{ 1 }{ x }dx \implies dx= xdu\]

Answer 9

Isn't du/dx = 1/x ?

Answer 10

Yeah you're both right :P

Answer 11

Ohh ahah right! I've lost my mind xD

Answer 12

This anonymous user who keeps joining makes me lose connection

Answer 13

kk so then.... \[-9\int\limits \frac{u^2}{x}(\frac{1}{x})du = -9\int\limits \frac{ u^2 }{ x^2 }du\]
right?

Answer 14

Which anon user? :O

Answer 15

Oh it shows up for me then I refresh haha...but when you do a u sub, you should not have any x's in your integrand

Answer 16

Well, unless you're just subbing in for du, then the x's should get cancelled out

Answer 17

\[-9 \int\limits \frac{ u^2 }{ x }xdu\] right/

Answer 18

Wait what just happened? o.o