Question

integrate x^3/(x^4+1)....seems like a partial fraction kind of problem but I can't find how to solve

Answer 1

\[\int\limits_{?}^{?}\frac{ y^3 }{ y^4 + 1}\]

Answer 2

there's a lot easier way
try to substitute
u= y^4+1

what do u get du as ?

Answer 3

I got half a page of the wrong answer.....I'll try the usub again brb

Answer 4

tell me what u get ?i may be able to point out the error..

Answer 5

wolf says my answer should be 1/4 ln(x^4 +1) ....

that wrong answer is a crumpled ball on the other side of the room i'm starting over

Answer 6

good,
so 1st step is to find du

Answer 7

ah dy = 1/(4x^3) so the x^3's cancel thats where I screwed up --- I didn't like the x^3 in the numerator and panicked

Answer 8

that is why an algorithm based on if you can't use usub try parts and then try fractions....me not being able to usub is a dodgy criteria

Answer 9

so you could solve this completely now right?
if you get stuck again, you can ask...

Answer 10

the integration is done....the differential solution is a different problem but I'll start a new Q if I can't figure out how that ='s sin(y) or maybe that is the answer....can't e both sides...does e^sin(x) mean anything...i'll work on it

thanks a ton

Answer 11

ok
welcome ^_^