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/sci/ - Science & Math

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6067015 No.6067015[DELETED]  [Reply] [Original]

What does /sci/ do when your limits are fucked after substitution?

>> No.6067023

Switch the limits and put a negative sign in front of the integral

>> No.6067022

>>6067015

Drop calc and take analysis.

>> No.6067031

>>6067023
Or just evaluate it as is...

>> No.6067078

>>6067022

it's not more difficult than Calc just more complicated.

I'd recommend it if you're confident your math, op

>> No.6067093

>>6067015
What's wrong with your limits? Integrating backwards? Oh no!

>> No.6067098

>>6067015
integrate and afterwards switch back to x's

>> No.6067106

>>6067098
you never have to do this for a definite integral. there's no point, it is a dummy variable.

>> No.6067109

Or you could just integrate by parts like a normal person would

>> No.6067115

>>6067106
Maybe I like to make my work look a little more complicated

>> No.6067126

>>6067115
>Maybe I like to make myself look a little more stupid

>> No.6067160
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6067160

>>6067109

>> No.6067162

>>6067109
>trivially easy problem
>MEMORIZE SOLUTION
rvivei affected

>> No.6067208

>>6067015
Why would you use substitution over integration by parts there?

Still, just evaluate as it is and switch to x whenever the fuck you fancy

>> No.6067230
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6067230

Also you forgot that ^5 on your u

>> No.6067231

>>6067162
>implying you have to memorize anything to integrate by parts..

oh.. you mean, YOU do? teehee..

>> No.6067253 [DELETED] 
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6067253

Hey, hate to be the guy but I've been struggling with this question for days and my midterm is in 6 hours now and I still have no idea how to do a question like this. I've went to /adv/ where they can only tell you how to get over a breakup, and looked everywhere for days, asked my useless prof still can't understand it

The question is, a 67.2g of Gold-Palladium alloy contains 2.49x10^23 atoms. What is the composition of mass of the alloy?

This was the closest thing I could find, but I'm unsure of how to solve.
Any help would be appreciated.

Moles mixture = 2.49 x 10^23/6.022 x 10^23 = 2.49/6.022
g/RAM gold + p/RAM palladium = moles mixture (above)
g + p = 68.4
Solve these two equations for g and p
where g = mass of gold; p = mass of palladium
Then % gold is g/67.2 x 100 and % palladium is p/67.2 x 100.

>> No.6067277

>>6067231
You... do realise that integration by parts is an algorithm right? If you don't know the algorithm you obviously can't do it. Of course you could develop the algorithm yourself, but developing a complex algorithm to solve a trivial problem is basically being a smart idiot.

>> No.6067626

>>6067208
Why the hell would I use IBP when it would require two integrations and substitution only requires one.

>> No.6067925

>>6067277
>integration by parts is an algorithm right
>developing a complex algorithm

uh, are you kidding ?

a) u'v=(uv)'-uv'
b) integrate

woa, so complex