Find constants of function I have this equality : 
$$f(x)=\frac{9}{(x-1)(x+2)^2}$$
I am required to find the constants A, B and C so that,
$$f(x) = \frac{A}{(x-1)} + \frac{B}{(x+2)} + \frac{C}{(x+2)^{2}} $$
How do we go about solving such a question? 
I am not sure on how to solve such questions. Approach and Hints to solve these kinds of questions are welcomed. :)
Thank you!
Edit:
Wow, saw all the answers! Didn't know that there were a lot of different ways to solve this question. Math is such a fascinating thing!

Algebric solution: use Euclide algorithm to solve the Bezout equation
$$
1 = (X-1)U(X) + (X+2)^2 V(X).
$$
Analytic solution:


*

*multiply by $x$ and take limit to $\infty$ gives
$$
A+B=0
$$

*multiply by $x^2$ and take limit to $\infty$ (after plugging $A+B=0$) gives
$$
0 = 2A-B+C
$$

*multiply by $(x-1)$ and take limit to $1$ gives
$$
A = \frac 9{3^2}=1.
$$


You then get $B=-1, C=-3$.
