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Calculus help

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E.C.
Posts: 3211 - Karma: 319
okay so im doing integration by parts and i just dont get it

the question is integrate x^7 ln(3x) dx

u= ln(3x)
du= 1/x dx

v= (x^8)/8
dv= x^7 dx

can someone help?

Dec 13 2010 2:49AM
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chardi
Posts: 5040 - Karma: 59
i'm so glad i don't have to take math anymore. good luck with that dude
Dec 13 2010 2:51AM
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Grodent87
Posts: 361 - Karma: 15
deriv of ln(3x) is 3/x
Dec 13 2010 2:52AM
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Grodent87
Posts: 361 - Karma: 15
shit nevermind no its not
Dec 13 2010 2:53AM
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E.C.
Posts: 3211 - Karma: 319
its the anitderiv. 3x/3
Dec 13 2010 2:53AM
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E.C.
Posts: 3211 - Karma: 319
3/3x woops
Dec 13 2010 2:57AM
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chicken
Posts: 6843 - Karma: 2,122
integrate by parts you can just plug into a formula. it's weird because substitution is so much like the chain rule, but by parts is totally new.

anyways i would solve it for you but wolfram can show you the steps better anyways...

http://www.wolframalpha.com/input/?i=integrate+x^7+ln%283x%29+dx
Dec 13 2010 3:02AM
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E.C.
Posts: 3211 - Karma: 319
i know the answer i jsut dont understand how to get to it
Dec 13 2010 3:07AM
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chicken
Posts: 6843 - Karma: 2,122
did you click "show steps?"

it pretty clearly shows the formula, the variables to choose, and then it all plugged in.
Dec 13 2010 3:26AM
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NOSNOWJUSTICE
Posts: 1176 - Karma: 83
I should be studying. But I'd rather to math. Weird?

Hope it helps...


Click for larger image
Dec 13 2010 3:31AM
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NOSNOWJUSTICE
Posts: 1176 - Karma: 83
DAMN THAT'S COOL!

Just finished my Calc 1, 2, and 3 series yesterday. Wish I knew of that... hahaha

damn....
Dec 13 2010 3:32AM
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chicken
Posts: 6843 - Karma: 2,122
yeah sometimes it does not show the steps that well. Super useful for so many things once you learn how to type it all in right.

plus it does other crazy stuff, this is the weather when i was born....

http://www.wolframalpha.com/input/?i=weather+january+9+1990+durban+south+africa
Dec 13 2010 3:55AM
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Style+eeze
Posts: 6901 - Karma: 551
Haha, I took AP Calc AB last year. I'm pretty glad I chose to take AP Stat instead of BC this year...
Dec 13 2010 3:55AM
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