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Sat 18 Feb, 2006 11:19 pm
Find S x(1-x^2)^4 dx using the subsitution u=1-x^2
S = integration symbol thing.
this is part of a maths assignment for integration cos we've finished the
topic but we havent learnt anything about subsitution. I'm completely
lost...where do i start? cos if you use the subsitution then you have an x
and a u in the same thing, how do you integrate with 2 pronumerals? i read
some stuff on the internet but it was really confusing.
Thanks for your
help!
oh, sheesh, something has gone terribly wrong
i actually did not write that post
what on earth....
i am gonna kill my sister - she is the only possible suspect
if your sister did write that post, theres no reason to tell the whole forum - it's a reasonable question. It's not like she's pretending you're insane or ruining your (non existent) reputation.
Here's an example of integration with substitution I found:
http://www.sosmath.com/calculus/integration/substitution/substitution.html
I don't know to do your question - hopefully someone else can help you!
thanks - i'll tell her
well, i always say stuff like that anyhow. and i didn't say it because i'm worried about my reputation - nothing like that. i just wrote it because...i did.
Did that link help you understand the problem? If not, post back and we'll get you through it.
according to my sister, she said that she didn't understand because it included pro-numerals
If u substitute in and change dx to du correctly the x's should cancel out leaving you with and integral just in terms of u.
If u = (1 - x^2) then du = -2x dx or dx = -du/2x.
You have to substitute in for both (1-x^2) and dx. The equation becomes (x)(u^4)(-du/2x) and the x's cancel out, leaving an equation only in terms of u. Now you can integrate it.
thankyou
will tell her (hopefully she'll understand now
)
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