Calculate Flux of Vector Field in Closed Surface | Divergence Problem Solution

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Homework Statement



Find the flux of the vector field out of the closed surface bounding the solid region x^2 + y^2 ≤ 16, 0 ≤ z ≤ 9, oriented outward.

F = x^3 + y^3 + z^3


Homework Equations





The Attempt at a Solution


I found the divergence which is 3x^2+3y^2+3z^2.

And then I'm stuck. I know Flux is divergence * Volume, in a simplifed way. So i factored 3 out, and i got 3(x^2+y^2) + 3z^2. I do not know where to go from here. Thanks in advance
 
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Integrate over the surface using the transformation to cylindrical co-ordinates, using x = square_root(16) cos(theta) and similarly for y, and the divergence theorem gives support to your integrating over the vector field, once you have added in the jacobian, from zero to two pi for theta, and from zero to 9 for z.
 
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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