Compute these integrals:

(1) $\displaystyle \int_{-\infty}^{\infty}$ $\displaystyle \frac{x^2}{x^4-4x^2+5}dx$

(2) $\displaystyle \int_{-\infty}^{\infty}$ $\displaystyle \frac{cos{\alpha}x}{(x^2+1)(x^2+4)}dx$

(3) $\displaystyle \int_{-\infty}^{\infty}$ $\displaystyle \frac{xsinx}{x^4+1}dx$

The first problem deals with an integral of a rational function. The other two deal with integrals over the real axis involving trig functions.

I am suppose to do these similar to the examples in my book. However, it is still complicated for me and I don't understand.. Any help would be greatly appreciated, thanks!