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!

Add the three fractions on the right hand side of your equation 
$$\frac{A}{(x-1)}+\frac{B}{(x+2)}+\frac{C}{(x+2)^2}=\frac{A(x+2)^2+B(x-1)(x+2)+C(x-1)}{(x-1)(x+2)^2}$$
I'll leave it to you to simplify the numerator and solve for $A$,$B$ and $C$, such that.
$$A(x+2)^2+B(x-1)(x+2)+C(x-1)=9$$
