分式的混合运算2m2-4m/(2-m)(m-1)-(1+m)/1-m2-1-a2/(a-1)-a-1-a2/(a-1)-a是（-1）-a2/(a-1)-a别看错题目啊
问题描述：
分式的混合运算
2m2-4m/(2-m)(m-1)-(1+m)/1-m2
-1-a2/(a-1)-a
-1-a2/(a-1)-a
是（-1）-a2/(a-1)-a
别看错题目啊
答
(2m^2-4m)/(2-m)(m-1)-(1+m)/(1-m^2)=2m(m-2)/(2-m)(m-1)-(1+m)/(1-m)(1+m)=-2m/(m-1)-1/(1-m)=(2m-1)/(1-m)(-1)-a^2)/(a-1)-a=(1-a-a^2-a^2+a)/(a-1)=-(2a^2-1)/(a-1)