Finding the Center of Mass of D

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Homework Statement


Let D be the region in the (x, y) plane bounded by the lines y=x, y=4x and the hyperboals xy=1 and xy=9. find the center of mass of D.


Homework Equations





The Attempt at a Solution



My thought: to use the center of mass formula? and use the change of variables?
 
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What have you done? The problem is to find a center of mass- why should there be a "?" on "use the center of mass formula"? Of course you shold use it. I can't speak toward "use the change of variables" because you haven't said what the integral is!


(Strictly speaking, this is NOT a "center of mass" problem at all because you have not given any density function so there is no "mass" and no "center of mass". It is a purely geometric "centroid" problem but that can be done exactly like a "center of mass" problem assuming constant density.)
 
HallsofIvy said:
What have you done? The problem is to find a center of mass- why should there be a "?" on "use the center of mass formula"? Of course you shold use it. I can't speak toward "use the change of variables" because you haven't said what the integral is!


(Strictly speaking, this is NOT a "center of mass" problem at all because you have not given any density function so there is no "mass" and no "center of mass". It is a purely geometric "centroid" problem but that can be done exactly like a "center of mass" problem assuming constant density.)

the problem is not given one.

do I have to find the area of the two regions first?

Then what do I do next?
 
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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