Question

Evaluate the indefinite integral:
7/(x(ln(7x)))

I've tried so many times but I just can't get it :(

Answer 1

let u=ln(7x)

Answer 2

\[\Large\bf\sf \int\limits \frac{7}{x \ln(7x)}\;dx \quad=\quad \int\limits \frac{1}{\ln(7x)}\left(\frac{7}{x}\;dx\right)\]Make the substitution mentioned above.
If you arrange the integral like this, maybe the du will jump out at you a lil easier.

Answer 3

Oh that didn't help.. I shouldn't had left the 7 in there :P my bad.

Answer 4

I got \[7\ln(\ln(7x))\] but apparently it's wrong...

Answer 5

Hmm that looks correct.. lemme see what's going on.

Answer 6

Thanks!! They gave this hint but I'm not sure how it'll help: NOTE: The absolute value of x has to be entered as abs(x).

Answer 7

Oh oh oh ok. Yah they're being a little fussy.

Recall this integral a sec:\[\Large\bf\sf \int\limits \frac{1}{x}\;dx \quad=\quad \ln|x|+c\]

Answer 8

Ohh I got it! They wanted me to enter it as\[7\ln \left| \ln \left| 7x \right| \right|\]

Thanks for your help!!

Answer 9

stupid absolute value...

Answer 10

Cool good job \c:/

I think it just be \(\Large\bf\sf 7ln(abs(ln(7x)))\)

Just absolute on the outer log.
I could be wrong though -_-