To start off with let 2/P(P-2)=A/P + B/(P-2) making the RHS of the equation one fraction gives : (A(P-2)+B(P))/P(P-2). So now we can compare the numerators (as the denominators are the same): A(P-2)+B(P)=2. This equation holds for any value of P so we can choose certain values for P that will help us find A and B. When P=0, -2A=2, so A=-1, and when P=2, 2B=2, so B=1. Then replacing A and B with the values we just found into the original equation gives: 2/P(P-2)=1/(P-2) - 1/P