Integrating by partial fraction.

azatkgz
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Homework Statement



\int \frac{dx}{(x+1)(x^2+1)(x^3+1)}



The Attempt at a Solution



I tried to solve it in 3 ways.
1)\frac{A}{(x+1)}+\frac{B}{(x^2+1)}+\frac{C}{(x^3+1)}

2)\frac{A}{(x+1)}+\frac{B+Dx}{(x^2+1)}+\frac{C+Ex}{(x^3+1)}

3)\frac{A}{(x+1)}+\frac{B+Dx}{(x^2+1)}+\frac{C+Ex+Fx^2}{(x^3+1)}
But it gives me nonsense.
 
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(x+1) divides (x^3+1). You can write the partial fraction with just linear and quadratic denominators.
 
Then should I solve in this way?

\frac{A}{(x+1)}+\frac{B+Dx}{(x^2+1)}+\frac{C}{(x+1)^2}+\frac{F+Ex}{(x^2-x+1)}
 
That looks ok to me.
 
damn this prob is going to be long
 
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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