B-c/(a+b)-ab-b^2/(a^2-ac)*a^2-c^2/a^2-b^2=b-c/a+b--b(a-b)/a(a---c)*(a-c)(a+c)/(a-b)(a+b)=b-c/a+b -b(a+c)/a(a+b)=a(b-c)-b(a+c)/a(a+b)=ab-ac-ab-bc/a(a+b)=-c(a+b)/a(a+b)= -c/a
a^2-4/x^2-9:a^2-2a/xy+3y+2-y/x-3=(a-2)(a+2)*y(x+3)/ (x-3)(x+3)*a(a-2)+2-y/x-3=y(a+2)/a(x-3)+2-y/x-3=2(y+a)/a(x-3)