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  #1  
Old 12-04-2017, 09:15 AM
ch1rontl34 ch1rontl34 is offline
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Default Integration question

Hi everyone, I'm working on an MLC question but the question is actually calculus related. It's been many years since I passed P (career changer) and I can't seem to figure out this integration problem

I understand what u substitution is but I don't know how setting u=10-rootx leads to the 2 in the numerator. The steps in the attached picture are incomplete for my understanding, can anyone please help? Thank you!
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Last edited by ch1rontl34; 12-04-2017 at 09:47 AM..
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Old 12-04-2017, 09:34 AM
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Klaymen Klaymen is offline
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Can't read the problem with a graphic that small. Try putting the image in paint and cropping out the important parts.
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Old 12-04-2017, 09:35 AM
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Gandalf Gandalf is offline
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Quote:
Originally Posted by ch1rontl34 View Post
Hi everyone, I'm working on an MLC question but the question is actually calculus related. It's been many years since I passed P (career changer) and I can't seem to figure out this integration problem

I understand what u substitution is but I don't know how setting u=10-rootx leads to the 2 in the numerator. The steps in the attached picture are incomplete for my understanding, can anyone please help? Thank you!
I can't see the picture clearly, but the 2 is probably associated with root x being x^(1/2) [and quite possibly then with the change of dx to du],
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Old 12-04-2017, 09:48 AM
ch1rontl34 ch1rontl34 is offline
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I have updated the attached file, sorry I didn't realize it showed up really small. I hope it's better now. Thanks to all who have responded already!
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Old 12-04-2017, 10:01 AM
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Gandalf Gandalf is offline
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Yes, what I expected. If

u = (10 - x^(1/2)) then

du/dx = -(1/2)x^(-1/2) so

du = -(1/2)[x^(-1/2)]dx

-2 du = [x^(-1/2)]dx

That last step is where the 2 comes from, also where the - in the numerator comes from.
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Old 12-04-2017, 10:06 AM
ch1rontl34 ch1rontl34 is offline
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I get it now, thanks Gandalf! I forgot about replacing dx in terms of du.
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