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Mathematics 20 Online
OpenStudy (anonymous):

how to solve this integral ? (given below)

OpenStudy (jhannybean):

which integral?

OpenStudy (mimi_x3):

\[\int ln(x^2)dx\]

OpenStudy (jhannybean):

Where did that come from lol.

OpenStudy (mimi_x3):

from meh. solve it bb ;)

OpenStudy (jhannybean):

u sub :)

OpenStudy (anonymous):

\[\int\limits \frac {v+v^2}{1-v^3} dv\]

OpenStudy (mimi_x3):

power series.

OpenStudy (mimi_x3):

break the integral up

OpenStudy (mimi_x3):

\[\int \frac{v}{1-v^2} + \frac{v^2}{1-v^3}\]

OpenStudy (mimi_x3):

typo...first integral is 1 - v^3

OpenStudy (mimi_x3):

u sub won't work for first integral

OpenStudy (mimi_x3):

u = 1 - v^3 => du / dv = -3v^2 while the the top is v, so it doesnt cancel out

OpenStudy (mimi_x3):

for the first integral^

OpenStudy (anonymous):

then what???

OpenStudy (mimi_x3):

ok the first approach is to break it up then partial fractions on the first integrand, then u -sub for the other integral second approach is to use partial fractions on the initial integral

OpenStudy (mimi_x3):

so which approach u want to choose

OpenStudy (anonymous):

1st one

OpenStudy (mimi_x3):

ok it's gonna be long partial fractions - ((1-v)/3(v^2+v+1) + 1/3(v-1)) complete the square , then u-sub on the next integrand

OpenStudy (anonymous):

the actual question was a differential eq: dy/dx = (x^2 + y^2 ) / (xy+ y^2) i used y = vx and came to the integral which i posted here ... was i correct ?

OpenStudy (anonymous):

@Mimi_x3

OpenStudy (kainui):

@digitalmonk I checked and got the exact same integral as you. Follow @Mimi_x3 's awesome advice and do it!

OpenStudy (perl):

so this question is a step in a bigger question

hartnn (hartnn):

ln (x^2) is 2 ln x right ? integral of ln x is pretty standard...or if needed to derive, use integration by parts :)

OpenStudy (anonymous):

\[I=\int\limits \left( \ln x^2 \right)*1 ~dx\] \[= \int\limits \left( 2 \ln x \right)*1 dx=2 \ln x *x- \int\limits \frac{ 2 }{ x }*x dx+c\] i think now you can complete.

OpenStudy (kainui):

@eliassaab Did you even read the damn question?

OpenStudy (kainui):

@eliassaab Don't make yourself look like more of a fool than you already are. ;P

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