help

subzero12

im still doing integration by partial fractions

the question i have is 3x/((2x-1)(x+3))
i got an answer of (3/14)*ln(2x - 1) + (9/7)*ln(x + 3) + c

you would be able to help me out by even leting me know im heading in the right direction thanks

Dufresne

Your answer is absolutely correct

subzero12

thanks for the help

so if i have 3/(2X^2+7X+3) with partial fractions

if i integrate it i get 3/2 (x^-2) + 3/7 (x^-1) + (1)

which gives me an answer of 18/5) ln (2x+1)/2 -(9/5) ln (x+3) +C
is that right ? and thanks for all the help ive gotten off the guys that are in here already its much appreciated

LeixlipRed

Yeh it's correct but remember if you differentiate your answer you will get the original function you had to integrate so try that check next time.

EDIT: first one is correct, didn't look at second.

Michael Collins

subzero12 wrote: »

thanks for the help
if i integrate it i get 3/2 (x^-2) + 3/7 (x^-1) + (1)

What's going on here? You can't split up the denominator like that... Also you haven't "integrated" it...

LeixlipRed

Yeh something dodgy going on there. Think he didn't mean to say integrate though.

What you need to do is factorise your quadratic. (2x + 1)(x + 3) is the factorisation. Then just replicate exactly the method from the previous question.