(3m的立方-4m平方+m)/m-m
问题描述：
(3m的立方-4m平方+m)/m-m
答
(3m的立方-4m平方+m)/m-m
=m(3m^2-4m+1)/m-m
=3m^2-4m+1-m
=3m^2-5m+1