why does integration by parts give a different answer so i know the answer for $\int{\frac{x \, dx}{(x+b)^{2}}} \quad \textrm{is} \quad \frac{b}{x+b} + ln|x+b| $
But i tried integration by parts and obtained the following, 
Setting $ u= x, \, du=dx, \, dv = \frac{dx}{(x+b)^{2}}, \, v=\frac{-1}{x+b} $ 
$ \int{\frac{x \, dx}{(x+b)^{2}}}= \frac{-x}{x+b} + ln|x+b|$
Does it have anything to do with any possible singularities in the integrand?

Both results are true, they just differ by a constant :
$$
\frac{-x}{x+b} + \ln|x+b|=\frac{-x-b+b}{x+b}+\ln|x+b|=\color{red}{-1}+\frac{b}{x+b}+\ln|x+b|.
$$
