Question

help! intergration by parts: when do you stop intergrating? If it is until your next intergration give you zero, then what about the special cases (e.g.: e^x) -- Thanks So much!

Answer 1

Hoot! You just asked your first question! Hang tight while I find people to answer it for you. You can thank people who give you good answers by clicking the 'Good Answer' button on the right!

Answer 2

Also, how do i bump?

Answer 3

use until you solve it :)
any example?

Answer 4

e.g.: when do i stop intergrating when i do intergration by parts

Answer 5

e.g. e^x is an infinite "loop"

Answer 6

\[\int\limits_{ }^{ }e ^{x}dx=e ^{x} +c\]

Answer 7

something like: \[\int\limits_{}^{} X^3*e^x\]

Answer 8

i get (x^3)(e^x) - (3x^2)(e^x)-6x*e^x-6x*e^x-6\[\int\limits_{}^{}e^x\]

Answer 9

and the last step is: -\[\int\limits_{}^{}6*e^x\]

Answer 10

so isn't that an infinte loop cause i gotta intergrate until i get zero

Answer 11

this will require few of those!
1) u=x^3, dv=e^x
\[=x ^{3}e ^{x}-3\int\limits_{ }^{}x ^{2}e ^{x}dx=...\]

Answer 12

i only know f(x) and g(x) method =(

Answer 13

\[=x ^{3}e ^{x}-3x ^{2}e ^{x}+6\int\limits_{ }^{}xe ^{x}=... and one more time.. will be done!\]

Answer 14

it's just a matter of names... g,f, u or v... what ever you call it.

Answer 15

but when i do intergration by parts, i never stop b/c i dont know when to. If my next intergration gets to zero, i know to stop, but there are infinte loops like e^x

Answer 16

i don't understand what you mean... :(
can you finish your example? it's not = 0

Answer 17

\[=x ^{3}e ^{x}-3x ^{2}e ^{x}+6xe ^{x}-6e ^{x}+const\]

Answer 18

kk so: when you intergrate something and you have to intergrate again and again, the only way i know to stop is when i hit zero. But i never stop when i intergrate something that is a "loop" like e^x (b/c u can derive e^x for ever and still get e^x). I'm confused when to stop intergrating something.

Answer 19

did you get how to do integration in your example?
Do you have another one that I can see what you mean?

Answer 20

yes i know the basics, but repitive intergration is where i run into trouble b/c i dont stop intergrating.

Answer 21

ill look for antother example

Answer 22

Normally I integrate until I find the solution. Even "loop" could be beneficial (like in sin^n & cos^n integration)...

Answer 23

but how do you know when to stop? that's my problem.

Answer 24

you don't... :) unless it can not be solved...
some integrals could be founded only by table or computer programming...
I don't think in regular Calculus program they will put something like that

Answer 25

so there is no hard fast rule? just stop when it can't be solved? if so im sooooooooooo stupid

Answer 26

no "fast "rules...that I know of :(
I just go by the "rule", that the problems in a book & on a test - have to have solution. In real life - bummer!

Answer 27

well thanks for all your help :) you rock

Answer 28

you too! if you got to Calculus... you rock!

Answer 29

nah u do, u can explain it :)

Answer 30

thnx & good luck!!

Answer 31

ty u 2