Rational Fraction decomposition

Hi there,

It is probably a really easy question but i am a bit rusty.

I would like basically to decompose :

**(1)**

I thus need to breakdown into simple elements:

Now I can't remember how to find out A, B and C.

I've already checked online and I understood that, for example to find B:

I should multiply the first fraction **(1)** by and then change x for -1. but if i do that it will cancel everything.

on the other hand, I can't understand how to find A.

Pretty sure it is quiet basic question but does anyone could explain me the method for this fraction.

Thanks in advance.