(a的平方+a-1/a+1)-(a的平方-3a+1/a-3)=[(a²+a)-1]/(a+1)-[(a²-3a)+1]/(a-3)=(a²+a)/(a+1)-1/(a+1)-(a²-3a)/(a-3)-1/(a-3)=a-1/(a+1)-a-1/(a-3)=-1/(a+1)-1/(a-3)=[-(a-3)-(a+1)]/(a+1)(a-3)=(2...