Why Does This Integral in a Cube Differ from Wolfram Alpha's Solution?

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This is part of an example solution to a problem about integrating a function in a [0,1]x[0,1]x[0,1] cube. I just don't understand how the midst function is integrated like in the attached picture. This is the same integral in wolfram alpha and it gives a different solution:
http://www.wolframalpha.com/input/?i=intg((yz^2)*e^(-xyz))
 

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aija said:
This is part of an example solution to a problem about integrating a function in a [0,1]x[0,1]x[0,1] cube. I just don't understand how the midst function is integrated like in the attached picture. This is the same integral in wolfram alpha and it gives a different solution:
http://www.wolframalpha.com/input/?i=intg((yz^2)*e^(-xyz))

If you're choosing to integrate over a nice cube, the order of integration does not matter I believe.

Your integration for dx is wrong. You may want to re-integrate it.
 
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Zondrina said:
If you're choosing to integrate over a nice cube, the order of integration does not matter I believe.

Your integration for dx is wrong. You may want to re-integrate it.
You mean the integral in the attachment is wrong? It's part of an example solution not done by me so I thought it would be right but it would help a lot to know that there is an error in the example solution.
 
aija said:
You mean the integral in the attachment is wrong? It's part of an example solution not done by me so I thought it would be right but it would help a lot to know that there is an error in the example solution.

Indeed, your first integration is really :

##\int_{0}^{1} \int_{0}^{1} \int_{0}^{1} yz^2e^{-xyz}dxdydz##
##= \int_{0}^{1} \int_{0}^{1} yz^2\int_{0}^{1} e^{-xyz}dxdydz##
##= \int_{0}^{1} \int_{0}^{1} z - ze^{-yz}dydz##

The rest shouldn't be too hard :)
 
Ok thanks, it's clear now
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...

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