1)AX/(X+Y)+ AY/(X+Y)=(AX+AY)/(X+Y)=A(X+Y)/(X+Y)=A
2)a/(a-1)-1/(a-1)=(a-1)/(a-1)=1
3)m^2/(m+n)-n^2(m+n)=m^2-n^2/(m+n)=(m-n)(m+n)/(m+n)=m-n
1) C/(C^2-9)+3/(C^2-9)=(C+3)/(C-3)(C+3)=1/(C-3)
2) 2/(1-X^2)-2X/(1-X^2)=2-2X/(1-X^2)=2(1-X)/(1-X)(1X)=2/(1+X)
3) 5P/(P^2-Q^2)+5Q/(P^2-Q^2) =(5P+5Q)/(P^2-Q^2)=5(P+Q)/(P-Q)(P+Q)=5/(P-Q)