Stuck on an Area Between Curves Question

Camronnba
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I have been asked to find the area between the following curves
f(x)= x^3 -9x^2 +18x and
g(x)= (-x)^3 +9x^2 -18x

I started out by finding the points of intersection, which I found to be 0, 3, and 6. I then integrated |f(x)-g(x)|and evaluated between 6 and 0. I got an answer of zero but it says I am wrong. I then tried evaluating between 0 and 3, and 3 and 6 and adding those together, again I get zero. After that I brought out my graphing calculator, and after viewing the graphs, 0 seems like a logical answer. I must be making a mistake somewhere, if someone could please steer me in the right direction it would be greatly appreciated. Thanks
 
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Nevermind, I should really pay attention to absolute value signs when I see them. haha
 
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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