How Do You Integrate Using Partial Fractions and Trig Substitution?

aselin0331
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Homework Statement


\int(5x+2)/(x^{2}+25)^{2}dx


Homework Equations





The Attempt at a Solution



\int5x/(x^{2}+25)^{2}dx+2\int1/(x^{2}+25)^{2}dx

I can integrate the first part using u substitution then I am stuck at the second part...my partial fraction answer is the same as the question when I use the Ax+b, Cx+D thing...

I think it looks like an arc tan but I don't know how to go from there..

Thank you!
 
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hi aselin0331! welcome to pf! :smile:

for the second integral, use a trig substitution :wink:
 
aselin0331 said:

Homework Statement


\int(5x+2)/(x^{2}+25)^{2}dx


Homework Equations





The Attempt at a Solution



\int5x/(x^{2}+25)^{2}dx+2\int1/(x^{2}+25)^{2}dx

I can integrate the first part using u substitution then I am stuck at the second part...my partial fraction answer is the same as the question when I use the Ax+b, Cx+D thing...

I think it looks like an arc tan but I don't know how to go from there..

Thank you!

A trig substitution will work. Let x = 5 tan t, so dx = 5 sec2(t) dt.
 
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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