1-y/1+y + y(y+6)(1+y)/(y^2-1)(6+y)=1-y/1+y + y(1+y)/y^2-1=1-y/1+y + Y(1+y)/(y-1)(y+1) = 1-y/1+y + y/1+y =1-y+y/1+y = 1/1+y
